Anyone who marries someone with existing children, has to accept that at sometime there will be issues that need addressing, in fact even when it is the natural father it still happens. My 2nd husband started giving me ultimatums re my adult children and I told him that whereas I would openly discuss any issue that he was not happy with, if he started making me choose between him and them, I would start to resent him just for putting me in that position. He continued and I divorced him for that and many other reasons. Unless there are issues with drugs, alcohol etc most of us would bend over backwards to help our kids whatever their age. I would advise that you both sit down with your daughter and have a 3 way chat, raise concerns etc Your husband should not be dictated to by his adult kids who should know better, if they are against you, they will use any excuse to cause a rift and that’s something else he has to address.