No, not too sensitive. Why are you cooking dinner for children who pretend you don't exist? DW doesn't want to "hear it"? Are you just the house servant?

And FWIW, change is something that must be wanted... by all parties involved. Sounds like the only one wanting change in your home is you.

Your wife is , silently, but very loud and clearly, telling you where you stand and your importance in your household. What were these children like towards you pre-marriage and pre-baby? No, you shouldn't expect "some of this" as a stepparent. While your skids don't necessarily have to accept you as a 'father figure' to them, there is no excuse to be disrespectful and rude. Your wife is allowing this ill behavior. While she can not make the children feel love towards you, she sure as h*ll can demand the children living in your home to show respect and manners. For starters, stop cooking for ungrateful brats.

It’s not going to get better. Not at there age.
You have to take caharge. You make dinner, you make what you want to make. Either they eat it or they on the one. They will not screw up your kitchen !!! They will not touch food for the next few days. It’s peanut butter !!!!
You will not discuss ther BM, when they are with her they can talk to her If anything is said, it’s. Your great mother doesn’t want you get over it. Birthday ! BM and SO problems, so is Christmas, Easter
All your efforts goes to your 18mo
Make them realize that 8 mo is number 1. And they fall somewhere behind

DW problem. She needs to listen, support you and start monitoring the situation. It is not okay for any partner to feel like an outsider particularly one where you are contributing directly to their care. Who cares whether skids actually like you or not, you are entitled to be spoken to with manners and respect instead of being ghosted in your own home.

OMG this is exactly how I feel and almost exactly the same situation. I have one skid (f 10) and no biokids. My skid did this exact thing to me for so long I literally snapped. I went the heck off on her... for better or worse. My wife's problem is that she has always (and everyone really) treated this kid like a adult/princess. She is a only child AND a only grandchild on both sides. Super spoiled.
I just had enough of walking into me, as if she didn't see me clearly standing there. Gently pushing me aside to get to her mother, my wife, as we walk around a store. Then there is the thing you talk about "Mom, ...." and the thing they do where my wife and I are both there to pick her up from what or where ever and skid says hello to mom, but ignores the heck out of me. (this one a half way fixed by talking to my wife and making her enforce a "hello" but the "hello" is either faked badly or mumbled)
So one day I had enough. Skid was doing this crap and it was getting worse. This particular day skid was adding the "mom don't love me" routine to it. She was asking to be let out of the car "to walk home". I (and anyone with any sense) could see this was a test to see if anyone cared. Of course my wife wouldn't let her out miles from home, but we live in the country on a dead end road that the two of them do walk for fitness. As we turn onto our road, skid STILL going on about being let out. Now 5 or so miles of this:
Skid: "I can walk. Let me out."
Wife and I: "No. That's crazy"
Skid: "Why? I can do what I want. Let me out!"
Me: "NO!"
Skid: "Why!?" x30
Me starting to boil saying to my wife: "She just can't stand to be in the car with me and wants to prove you will dump her out so she can tell her therapist *yes skid gets therapy* you dumped her out"
Skid: Silent

As we pull in our quiet road, skid says again "Let me out! I want to walk home". My wife listens to me (which drives skid crazy) and we were home three doors later. Before the car is turned off skid is going on a rant about how she can do what she wants and she doesn't understand why we wouldn't let her walk from the next town over and yada yada.

I got out, slammed the door (totally not my usual thing). I screamed at her that I know she hates me and wants me to just go away but this is my house, she is a child who does not have free will - despite all the horrible parenting she has always had. I went on with "we will see who lasts longer" because "it's only a matter of time"... "You think because you win little battles here and there that you will win the war? I'll be with your mother the rest of her days. You, however, will be gone in 8 years and out of my house. Now get your @ss in your room."

I turned to my wife and thought I just costed myself my marriage. She was mad alright, but after a hour I had skid come out to finish this by talking, not yelling. She admitted, in front of her mother, how she (my wife is hard of hearing) would mumble things like "shut up" and "f u" to me so that my reaction seemed over the top to my wife. She admitted how she would do all sorts of things to make me feel unwelcome in my own home.

My wife appologized to me after.

Why am I back on step talk then? It lasted about 3 months. I see the trend going back to the way it was. My skid is a special case in the way she pits adults against each other and is fake as heck. Honestly do not have a clue what she likes and doesn't like because it changes with who she is talking to. Anyways, I honestly do not want to have a relationship with my skid. I just want peace and not have someone in my house trying to be a wedge between my wife and I. She and I have a longer history than skid has been on the planet, which I think adds to our issues. To make that long story short, we were high school sweethearts - never out of love - she was just raised to be married to a white man and go to the right church and have kids and be that person. She tried it, had skid, got beat, got divorced, and called me. Here we are.

Sorry for writting so much... I write a lot and speak very little in person.

I did not read the comments, way to excited to answer lol...

Skids ignores you, ignore them right back,

you cook dinner and they walk past you and ask their mum what's for dinner... ignore it, if she asks you what's for dinner to answer them, smile and say food......

stop paying for anything involving the skids, that's up to their parents to resolve and make sure DW pulls her financial weight at home, she pays 50% of your baby's stuff and all house hold expenses... nothing less. If her children wants special snacks, she buys it and they share with baby.

Simply ignore the skids, they are mere visitors in your home,

You realize your DW is encouraging their behavior unknowingly? When you are alone with her, bring little things up to talk to her about, small things, and simply say, Hon why aren't the kids asking the person who cooks what's for dinner, why do they ask some one who's not cooking?

Disengaging would probably be best for your mental well being right now. Perhaps in time they will come to you to have a relationship at which point you can re-evaluate the situation. I think the bigger problem is with your wife who is invalidating your feeling which I don't think is EVER acceptable. Your human and you feel how you feel. We don't get to choose our feelings. Only how we react to them so if the kids won't or can't have a relationship with you or even acknowledge you or appreciate you then disengage and spare your energy. I'm sorry you are going through this. Don't let your wife paint you into a corner though. It is disrespectful and not very loving in my opinion.

To answer your question, it is NOT normal for a skid to ignore the step parent. My SD17 always says hi when I get in, or when she does and I'm already there (I don't live with my SO).

My SO would be pissed if his DD did that to me and he would address it.

At their age, it is not unusual. My bio sons didn't like my DH at first and made it known. After they understood that I would not tolerate any bad treatment to anyone, especially my DH, they eventually came around and had great respect for DH. If your spouse does not make them respect you, you can just disengage and let them take care of themselves and let your DH take the blunt of their rudeness.

Just parent by example. I still do that. My SD57 has never liked me and made absolutely no bones about it. I just ignore her and have always been civil. After 30+ years, I totally disengaged, again with civility. SD57 hates me more today than ever, but that was never my problem, because I tried very hard with her and know I did the best I could do. I never had words with her and I let her be who she is. I never enabled her and I always tried to set an example of manners and maturity. She has neither to this day.

It will get better for you, if you move forward and don't tolerate bad treatment to yourself. This is what I do. It's not easy, but if you take yourself away from the hostility, it sends a message.

Reading these comments makes me realize skids' bad behavior generally manifests as junior high mean-girl tactics - I've suffered it too. Mean girls don't usually strike with fists - they shun, ostracize, manipulate the social scene against whoever they want to destroy. And it works. It's so slight and nuanced, unless you're on the receiving end, it's easy to miss, so the bioparents are blissfully unaware of the dynamic.

Figure out how to get ahead of a junior high mean girl and you'll probably have no trouble being a stepparent. But has anyone figured out how to get ahead of a junior high mean girl?

I lived in a similar situtation for 12 years; I married DH with SD6 at the time and was completely ignored unless either of them wanted something. Then, DH and I had 2 children so I spent most of my time concentrating on them. DH would get so pissed at me but if I tried to do anything with SD, I "wasn't her mother".  If I didn't do anything for her, I "wasn't treating her like I treated my kids".  It was damned if you do, damned if you don't.  I finally stood up for myself with DH; in fact the fight was so bad we almost got divorced.  But, when they both realized I was serious and willing to take it to a divorce court, their attitudes changed . Things improved a great deal after that fight surprisingly.  DH learned that I wasn't going to put up with their disrespect anymore and they both stopped treating me like I was an outsider in my own house.

The problem is that you will continue to do for your Skids and they will walk all over you without any consequences and their mother allows it. Hand them back over to their mom; if your wife and skids cannot treat you as an equal parent, then you don't feel obligated to do things that a parent would do such as give them rides to school. She has to be responsible for them 100%. I know you don't want problems with your wife but until you draw that line in the sand, they will continue to treat you like you don't exist unless they want something you can provide. 

No, it only gets worse in this dynamic with a weakling dadeee.  Adult step antics make the little ones look gracious; the bigger they are the bigger the issues -but only if you allow yourself to be caught up in your husband's emotional sickness.

My Skids would do the same exact thing to me. We would be sitting at the table and it's like i  was invisible. they were direct any questions do their dad. I got to the point where I literally got my plate and went to my room! In my eyes i would rather eat alone than sit at a table where i was being ignored! It was miserable. Now I am to the point were I just sit down eat my food than head to my room. I don't try to conversate with them or interact with them. I tried all these things early  on and it didn't seem to make anything better. I know the feeling of being a stranger in your own home all too well! It sucks! :(  I'm new to this site but i've learned a bit about disengaging and seems like a good idea....i'm still trying to brush up before full implementation. Good luck! 

If will never get better if you do not stop tolerating anything less than standards of reasonable behavior in your marriage and home. If what is happening now isn't working... do something different.

I take the direct confrontation approach to any violations of reasonable behavior. I set the standards for what is reasonable and if those standards are violated I bring escalating consequences to bear and insure a state of abject misery for the violator ... until their behavior returns to a state of compliance.

If they are rude... grab them by an ear, give it a twist, march them to an isolated corner, plant their nose in contact with the intersecting verticle planes, swat them on the ass  and they stand there until you get tired.

Lather, rinse, repeat.

Don't tolerate the crap, apply escalating consequences and the behavior will improve.  No need to overcomplicate things. The why of their behaviors is irrelevent. The what is easily identifiable and easy to address.  Focus on the behavior.  Don't give a crap about the why.

IMHO of course.

Good luck.