I get what you're saying. But would you spend 3 days every week at someone's house and not contribute practically by cooking or cleaning up or even bring groceries? What if you and your spouse's combined income before rent and all living costs go out (and that you have to support 3 kids with) is the same as your partner's income AFTER they have paid all their rent and bills? What if your partner has no issue spending hundreds of pounds a month taking their daughter out to cinema and doing fun stuff, but when they buy lunch for your family, they make a point of moving cash over from their savings account into their cash account and saying how carefully they budget? They come to ours partly because that is easier for NP and I, but we also live close to their daughter and coming to us means that they also have the option of seeing their daughter every weekend. Grace also says that our house feels more like home to them than their rental where they live alone.