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?
This is not a normal thing here in my place so I would never be in his shoes. Plus, I already declared to my parents and to my siblings how much I own, so in order to save him from declaring in front of everyone, he can declare the assets to his parents in private or to his siblings too if wanted to.
This is totally their family business I have no judgement to make, it can be easily solved because the person here is dealing with the family and if he doesn't feel comfortable, then only tell those whom he feels comfortable with, like parents or siblings. It is not a big deal as I said. Maybe the person in question holds more BTC than his brother's businesses and he fears that their relatives will think he is going to risk all that money in BTC and that is also a good consideration, therefore, he should show them something they want to see.
One thing you should know is that everybody is not always the same, what if probably he ask those his extended family members to leave that he want to be lift with his family alone, what is after declaring his crypto asset to his family maybe his family members still went ahead to review everything to those thier extended family what will you do?
That is why in a situation like this you need to think twice, because it has to do with the extended family not your family alone. had it been is your family alone that would've been a different case, But since it involves the extended family of course safety precautions need to be taken because no one knows what will be thier intention probably after declaring your crypto asset to them.