Hi Marcela,
Have you had a conversation with him and clarified what his feelings are aobut your relationship with his kids?
It sounds like there is a significant amount of tension in those relationships. What does your other half see as your role? What do his grown kids see as your role with them?
It sounds like from your other post, that you are having some issues with his kids.
If they don't agree with some of your parenting decisions on how you raised your son John, then you offering unsolicited advice (even if they are struggling, or seemingly in need of help) will be unwanted. If they see you as meddling and overbearing, his response may be to raise his voice to you because he feels he has no other option to get you to stop. Not ideal, but I don't know the full dynamic.
In that case YOU are the one who can stop the tension.... don't offer them advice or tell them what to do.
I think it is too much for you to expect him to take YOUR side over his KIDS. His FIRST allegiance SHOULD be to his kids, not to you. If you didn't want that dynamic, you might have done better with a mate that didn't have any children. I would hope that if he got into a squirmish with your kids, that you would stand up for your kids first.
Although, you don't indicate that is what he's doing, it almost seems like he isn't taking anyone's side - which may be the most allegiance he can give you in cases where the disagreement is between his wife and his children.
Quite frankly...... if my partner indicated his expectation was that I back him in arguments he was having with my daughter, I'm not sure I would stay in the relationship -that would be a deal breaker for me. But my daughter is 11, so my partner choice reflects a desire for us to be a "family" rather than if she were already an adult and out of the house living on her own. But even after she is grown, I am still her parent and unless she does something that is completely out of line, or boarders on mentally ill... .my first priority is to her.
Also, he shouldn't be the one to confront his son's wife (in the case about your daughter and the icing). That's his son's job.... or yours since she insulted your daughter. A swift, "please don't call my child names" from you would have been in order and, quite frankly, when my mamabear claws come out - EVERYONE had better run, partner included.
But obviously, his family doesn't seem to think much of you, warranted or not. THAT would be what I would focus on. Trying to correc the perception that they don't want to raise their kids the same way you raised yours. That's a bit harsh, but I think you may be focusing on the wrong thing, is my point.
I would urge you to have a conversation with your other half about what his expectations are.... what your expectations are.... and how you might be able to close the gap. It sounds like you don't have the same expectations, which will lead to disappointment for both of you.
Good Luck