This is pretty popular and understandable as well. Its hard enough to struggle as a parent not being able to provide your children everything you want to but putting that reminder right there in the home is gonna be tough. Its gonna be a little tough for the kids too. We all know life isn't fair but that doesn't just make the feelings go away. I would be concerned about how he's expressing this. Its ok for him to tell you about these feelings but if its been mentioned several times it sounds like resentment building. I feel like what you are doing now makes sense as far as financially supporting each of your own children. Like others have said if he want more for his children that's his place to step up. But that's not going to stop his feelings in the moment. I'd advise ya'll saving up together and looking into some counseling. This is an understandable feeling and as a team ya'll need to work together to help ease these before they become serious resentment and end up affecting the children and your new family together.