If you have a good relationship, then you should bring it up. But in a gentle way. I would just ask him general questions about his dating...
Does he want to date now?
Why hasn't he dated in years?
If his answers don't reassure you that he is heterosexual, then ask him if he's gay. The question is, are you okay with that? If so, this will be easy....then you can say something like, "Honey, sorry if I'm way off track here, but it's okay if you would rather date men."
If you're not okay with it, it would still be best to try to accept it and not judge him. Then you could use the same approach. I hope this helps.
Let me know if you have other questions. Take care.
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