Well for me I believe that even if the mentor is an immediate family member like a brother or a sister, there will still be a limit to what they can share with you, not necessarily because of selfishness. Rather because there are some things that cannot be fully taught.

You know people spend years trying to carve out their own strategies through series of trial and error. And most times that strategy that works for them may not work for another. This is simply one of the Irony in the crypto space. that is why it is very dangerous to depend solely on someone else's signals, without researching it out yourself.

Mentors be it family members or an outsider can only guide, one still has to walk his own path and learn his own way. So not only should we not trust our mentors we shouldn't also "fully" depend on them. Full dependacy cripples one's ability to learn.