A recent family event and a friend's comments shows how complex this situation can be.
We tell friends things we wouldn't tell family. Then there's what we tell some friends but not others.
Know it sounds complicated but I think it can be summed up as knowing your audience. Trust, empathy, brain connection all have a part to play in why we open up to some people and not others.
Of course, there are those who have no filter whatsoever and think they have to tell everyone everything about their lives.