I wouldn't marry a guy that stoops to "low blows" in fights.  I'm not saying that I don't ever have a disagreement with my DH.. but we don't say things like that.  If he truly believes that he can't love you at least "equally"  (but in different ways of love).. then you and he really aren't right together.

Wow he actually said that? Did he say that within earshot of sd10? It looks like she has won the competitionthat she is put you in.

I feel bad for you and the other two girls because he's probably neglecting them a little bit in favor of his older daughter. He sounds like an asshole for encouraging this competition and telling you that he's always going to love sd10 more. I really would have asked him at that point what about your other daughters? Tween girls are the absolute worst.

Uhh no he does not understand that there are different types of love and he is fully capable of loving you just as much as his own children. I would hold off on sealing that deal until he can get some therapy and learn the difference. I mean really so he holds his love for you to the same standard as his 10 year old daughter, that's a lot gross.

I'm guessing his daughter being older has the most memory of her family before they split.. and was likely put in the role of "woman of the house" once the split happened.  She is insecure and jealous of you being there.. so she is competing with you..  it sounds like you are "competing back" to an extent.

While I don't believe kids should dictate their parent's relationship.. I will caution against entering one where a child appears wildly opposed.. you "can" swim against a current.. but it's hard.

And.. what did he say about you being like SD.. was it a positive or negative comparison? If it was positive.. he is likely trying to point out to you that you and his daughter may share commonalities.. trying to show you that you are not too different. because he wants you to get along better.

At the point when he said that to you - I would be sticking my engagement ring where the sun don't shine!! 

OP---sorry your boyfriend told you that.

I would ask ahole if he loves the neighbors kid equal to his own bio kid. Use the neighbor kids name.

OP, expect to hear a  response such as "Why would I,  blah blah is not my kid."

Just let that sink in OP.

**so many people mis-use the word love on a daily basis** Love you, Love YOU, love you, LOVE YOUUUUUUUUUUU

Love is not a feeling- it is an action.

The love a father feels for his child and the love a man feels for his wife/wife to be are completely different.  There should never be a need to compare them or think about whether you love a spouse more than a child.  That is simply ridiculous.  It seems to me that your fiance either truly does believe these loves are on the same scale, or he was trying to intentionally hurt you.  Neither bodes well for the relationship.

I debated posting here because I don't think you are going to like what I say.  But hopefully it can help you.  

It sounds like you are very jealous of this SD and you want your SO to tell you that he loves you more than her so he had to point out that he will never tell you that.  

Don't tell your SO that you don't like his kid.  Don't compete with her.  Don't tell SO that you think SD is trying to make you jealous.  (That just sounds weird) Don't take offense when SO says something so trivial as "you did something like SD" 

This child is only 10 and she already knows that you are jealous of her.  Just wait until she is 13-14-15-16.  If she thinks it is a competition...she will REALLY make it a competition.  Just ignore it and I bet she will back off some.  

Absolutely tell DH to NOT compare you to BM.  

Im so sorry he said this, this is an unacceptable thing to say. I understand how you feel right now, for I have been told this as well. 

These parents dont understand it breeds resentment. Towards everything. 

It sounds like the dysfunction in that house is a recipe for step-hell. I'm not in a perfect situation either, and i know "just leave" is easier said than done. But....please don't move forward in the relationship or give up any more of yourself until the issue with SD is sorted out. To a situation that makes you feel respected, loved, and in a position where your needs as a person outweigh his need to cater to his daughter's wants. It sounds like he has some issues with his daughter that need to be worked out before he can be the husband you need. 

He told you that you are not his love and priority. Believe him.  As soon as that idiocy left his lips you should have dialed a lock smith to come rekey the locks and told him that he has until the lock smith arrives to pack his shit and the shit of his shallow and polluted gene pool and to GTF out of your home.

A child should never be the priority over a spouse.  And your SO's incesstuous bullshit makes he and his spawn a collective write off IMHO.

Move on, let them rot on the curb out of your life.  All of them.

Enjoy your new life with this POS and his shallow and polluted gene pool far in your rear view mirror.

It would be a very long time, if ever again, that I would be intimate with such a man.

Maybe he can turn to his beloved for more comfort.

Young and in love.  As time goes on it will get worst .  If you are starting here how must worst can it get.  He is putting DD over you. That no way to live.  She is only 10 it's only going to get worst as she gets older.  I don't know how often you have SK.  But remember having SK full time is only one BM accident away.  
Then what? 

I think everyone else already covered that hes an a**, but I just wanted to add that I think the fact that you dont have kids makes it even worse. For example, if my DH said that to me I could respond with "I feel the same." You cant say anything like that back to him and he knows it. That seems like a power/control move to me almost. Like he can go that low to hurt you and he probably feels more comfortable doing it knowing that for you you are his number one. So you dont have anything like that on him that you could say.

My husband has always said to me that he can make more children but he can't make another wife like me. 

Your husband is an idiot. It could have been a thing he said in the heat of the moment or he could have meant it. Either way you two need to work on your communication. There are ways in which a couple could have had the conversation you wanted to have (not being compared constantly) without it turning into an argument. 

Learning how to argue fairly is a skill. Sometimes we can work it out ourselves and sometimes couples need professional help to find ways to disagree and argue without always going for the jugular. Having a calm and open debrief of the argument can help, if that is possible. I know that in doing this with my husband I have learnt now that cruel insults that I had previously thrown in arguments cut him deeply and I do not use them any longer. 

You won't, but you need to cut and run while you can.  You'll regret the years lost if you don't.