While there's an understandable level of protection from parents concerning their child's romantic partners in high school or early adulthood, once your kid is almost thirty, it can be pretty ridiculous to enforce a "can't share a bed until you're married" house rule. Many people choose to never get married but still have a loving and supportive longterm partner, and not allowing two people who live together to share a bed just because they never had a big, white, expensive party is disrespectful to your adult children. Still, if religious reasons or family traditions prevent you from letting your adult child share a bedroom at your house despite the fact that they already have three kids and a dog together, the "my house, my rules" approach can be enforced if you wish. However, don't expect your kids to visit very often.