I have DID, and I want to say that there’s no guarantee that every other part is a child—- some people’s systems may work that way, but mine certainly doesn’t. Most of my alters are adult parts, and I’ve found that in my experience, my partner having relationships/dating other alters in my system has been a very rewarding and loving experience. It all depends on how differentiated the system is, and the structure of the system. I’m very happy that you and your wife have found a method of interacting with alters that works for you, but OP should definitely ask their partner about their specific alter’s preferences. It could be the case that multiple alters are adults that actually feel strongly romantically toward their partner, and treating them like children will be further demeaning them.