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?
If I were in your friend's shoes, I would do the same thing he did by not declaring his asset in bitcoin to his family and extended family. Since your friend is responsible for his well-being and is not getting any help from his three brothers, who are successful in their businesses, it is better for him not to let any of them know how much he is holding in his bitcoin portfolio so that his family won't come up with a plan that will ruin his plans he has with his bitcoin portfolio. One of the reasons why bitcoin was developed is that no one or government entity can be able to spy on us to know how much we are worth, so if you friend declares how much he is worth in bitcoin, he is only putting his life at risk because he can possibly be a target for kidnappers and scammers.