If you were in his shoes, can you declare your crypto asset to your family? Or do you think he should have declared it to them after the extended family members must have left and even if he did, the information can still leak to the extended family and from there it can escalate to other people. What opinion do you have to give in this situation?
I believe this person is an adult which I think his decision is his rules. For me I don't think it is proper for his family members to request for him to declare his asset to them because it might not be really comfortable him. Let just say he declares his asset to his family members and they see what is there, as something reasonable, who knows he can be pressure by the family to sell his bitcoin to fiat and won't be able to achieve his targets and plans. Bitcoin hodling is a personal investment which do not make sense to showcase it to people be it family members.
I don't think he is doing the wrong thing, aside bitcoin, if it were to be a saving in fiat and he decides not to tell his family members how much so far he has been able to save, I don't think it is wrong too so far as he is an adult.