A “No” reply would have been easy to deal with.
A “Yes”, I would ask if your state’s laws recognize him as a guardian.
Since this is about tenting, I don’t envy you having to determine this one, as the Cub in question may well look at him as a father figure and might not understand why he (the Cub himself) is being treated differently.
I feel like the Guide to Safe Scouting bounces between using guardian and legal guardian. So, it seems at times it specifically talks of guardian vs. legal guardian.
It may be good to register the boyfriend. For sure he could be the another registered adult. 2 cubs, one being a tiger, makes it harder.