Blended family

So... me and my fiancé have been together for going on 3 years. He has a 5 year old and I have a 7 year old both from previous relationships and an 8 month old baby girl together .

When we would break up he would have nothing to do with my son or our daughter and was an amazing father to his son.

When we get back together he shows his son a different love than he shows my son and our daughter.

He has cute nicknames for his son and doesn’t for my son.

When we got together he made it a point to say that he would adopt my son as his own and love him as his own.

We recently moved into his home with his family and they all only show love and affection to his son and but barely show love and affection or talk much at all to my son and our daughter.

I’m struggling with it because when I bring it up he says I’ll always have this problem comparing the kids and I’ll never grow up from this

But as a mom I know he shows the kids different love and affection he kisses and loves on his son and nothing to my son it bothers me because he promised me he would love him as his own and he never has.

I love and care for all the food