Yes, when family members are living together in one household, everyone needs to chip in. They're partaking of the expenses of your household, so it's better for everyone if they
pay room and board at a going rate you all agree on. Many adult children make the mistake of thinking short-term and saying, "I can't charge Mom and Dad rent," but believe me, sharing expenses will help avoid resentment and conflict in the long run. It gives parents a sense of both responsibility and pride, and they're less likely to feel like a burden.
It also gives the older adult a voice. As rent payers, they're entitled to make requests and help make decisions, including those that affect the household budget. For example, Dad might say he wants red meat at dinner a couple of times a week. Maybe he doesn't get steak if that's not in the budget, but he gets hamburger or meatloaf.
When parents pay rent, it also makes it easier to work out disputes, such as how high to turn the heat. A common point of conflict is that the parents want to run the heat all day, and the adult child can't afford the utility bill. If parents are paying room and board, they can offer to pay a little more to keep the heat up, if that's what they want. Or everyone can work out an affordable compromise.