Yes, your 5 year old is certainly capable of trying to make his sister jealous. You need to talk to him and tell him it's naughty. You should also be redirecting his "daddy daddy daddy" show when SD is around.

Yeah, your five year old sure can be doing exactly what he's being accused of.

Think about it. You just made an issue about 'mini wife' thing an it's a no no now for her father to cuddle up with her... but where was your son this weekend? Oh, right, cuddled up on the sofa with with you and his stepson.

Do you seriously believe this boy is too 'innocent' not to realize he has been rewarded with the exact same spot you banned SD from? 

Go sit in a classroom of kindergarten kids for the day and observe their interactions. You'll see exactly what five year olds are capable of in their socialization and interaction with others (how selfish, self centered and ha-ha I'm better than you ).  

1.  Talk to your son.  Tell him to knock it off.  Tell him when you are around, he comes to you.  If he keeps up the gloating and teasing, time out for him. 

2. Talk to DH, get him to spend more time with his DD when she is there. 

"Think about it. You just made an issue about 'mini wife' thing an it's a no no now for her father to cuddle up with her... but where was your son this weekend? Oh, right, cuddled up on the sofa with with you and his stepson.

Do you seriously believe this boy is too 'innocent' not to realize he has been rewarded with the exact same spot you banned SD from? "

i really hope you read this over and over again.  You gave your husband grief for cuddling with his bio.  However, you have no issue at all with him cuddling with his stepson.  Why didn't you or your husband think to include SD?

Both kids have picked up on what is going on and they both are reacting to it. 

SD is bullying your son because she feels like she is being replaced by him.  Your son is gloating because he has more time with her father than she does.

You and your husband need to fix this.  You fix this by telling your son to stop being an ass.   

Your argument that she shows no jealousy towards the baby doesn't wash. The baby is not a threat to her yet. All it does so far is eat, sleep, scream and poop and most men do not fawn over newborns and have them as hip babies so naturally your stepdaughter doesn't see the bond between her dad and the baby as a threat...for now. It will come. 

As for your son, of course he could be doing these things. We read stories here all the time of children of that age range being completely manipulative. If you want to help have a family meeting with all of them there and call it out. He needs to tell his daughter to stop with jealousy and spitefulness. If she wants to spend time with her dad then she needs to speak up instead of over-reacting when she sees the boy doing it. You need to tell your son that he needs to stop hanging all over your SO. If he needs something then he needs to either ask you or get it himself. You both need to stop with the mini-child syndrome that the kids are playing off of each other. I also agree that to you both need to tell them how you plan on fixing the problem: your SO needs to spend time with his daughter alone while she is there and you need to start jumping in and helping your son whenever he tries to start monopolizing your SO. 

Plenty of older kids, even in intact families, can be jealous of a baby.  I suspect not here, because OP is doing most of baby care, not dad.  

I disagree with dad stomping on his DD.  She is not the one creating the problem.  The road to stopping this is the son must stop the teasing, mom must say it must stop, no sitting next to dad by either kid, and dad must spend more time with his DD. 

Make it clear that no one is sleeping with daddy but mommy.  

Since you know this is going to happen head it off at the pass. Have your 5 yr old be busy and engaged in other stuff or he can have a friend over to break up the dynamic when SD is there.  Maybe he could even spend a night at grandmas. Since sd is there so little it may be nice for her and her father to have some one on one time before heading to your home. They could go to lunch or do some shopping on the way.

Talk to your kid, he obviously feels threatened by sd's presence and is being mean.  DH should talk to SD, make known that her place in the family is secure. He is her dad and she needs to learn how to be mature and not react to a 5 yr old's antics.  Most of the time this kind of behavior will go away if it's ignored.  

Your 5 year old can absolutely be purposely doing this to annoy SD and make her jealous.  My SO has a 5 year old daughter and, while I love her dearly, that kid has manipulation skills like you would not believe.  I'd put her up against an adult any day.  Don't think that because he's young he doesn't know what he's doing.  He probably knows EXACTLY what he's doing and is doing it for effect.  Tell him you know what he's doing and he needs to cut it out.  Impose consequences.  And tell your husband to spend some quality time (not cuddling time) with his daughter.

Lol, this is my youngest to a tee, except none of the kids get jealous of him because they know what he’s doing.  What I would do is validate your SD and empathize with her in front of your son.  If she understands what he is doing and why, and that you all know it too, your DS will lose his power, and she won’t be as angry. 

a 5yo and an 11yo.  I see this as sibling rivalry at its worst.  He's a pretty smart little guy to figure out how to push her buttons.  

I think you two adults need to take a step back and figure out what your parenting message is to all the kids in your house.  Don't let them pull you into their childish dysfunction.  You and DH set the tone and rules in your home and they should all support a functioning  healthy family .  

Nip it in the bud when it is happening, not after, not after tattling, not after the kids are trying to you on their side.  Decide on what you say each and everytime loyality is questioned.  "there's enough love for everyone", we treat everyone in this house as family, etc..... what ever you and DH come up with that is your family motto.  

Each kid is looking for security from the adults, give it to them but don't give into their game playing.  

I don’t think commenters are trying to be harsh toward your 5-year-old...just trying to open your eyes to see that yes...he’s perfectly capable of this behavior...for whatever reason or no reason at all. 

Personally, I don’t think it’s unusual or terribly awful behavior and certainly doesn’t warrant meltdowns or full family counseling. Siblings and other kids get jealous of each other and try to tease and get a rise out of each other all the time.

I recently took my niece and two nephews out...the oldest nephew (12) is my sister’s full-time stepson and the other two (girl, 9 and boy, 5) are her kids. These three are crazy about each other...especially the youngest boy about his older brother...he idolizes him and they do a lot together. But At some point in the night, my sister’s two kids ganged up on their older half-brother calling him by his full name in a sing-song voice (He used to have a different last name and it really bothered him. My sister and her husband legally changed it last month.) As soon as I realized what was happening I told them to knock it off...and I was shocked and it hurt my heart a bit. They’re all usually very good to each other and I love taking them out and spending time with them because of it. But yes...for some reason that I don’t know my sweet, beautiful niece and my adorable, loving nephew were being total shits to their big brother. I don’t think that makes them terrible kids...it just makes them kids. And they had to knock it off and I told their parents :-/ 

In your case...it should certainly be corrected...but no need to act like it’s the end of the world. Your son likely called your husband daddy one time, as he’s used to doing, and saw that it got a reaction from his stepsister...so he did it again...that’s how kids are. Have you ever noticed how kids want you to say or do something funny a thousand times in a row? (At least...my 5 and under nephews are this way). I almost don’t want to make my nephews laugh because I know they’ll ask me to do that same thing a gazillion more times and laugh just as hard every time. They like to experiment and repeat things and see how the people around them react.

i also don’t think that you’re trying to make your DH “play daddy” to your son. You live together full-time and it seems he cares for your son. That’s perfectly fine. Just be mindful of your SDs feelings...and assure all kids that they’re loved and have a place in your home. No need to compete.