>>Most of their regrets revolved around their family and how they wish relationships, usually either with their children or between their children
I am willing to bet, that if you met many of these people in the 40's and 50;'s (where I am today) they would have the same statements.
I too sometimes regret I am not closer with family, or have more "friends" but at the same time I do not have the desire to change that reality at all...
It is complex psychological problem for me I have always since my teens been a "loner", I do not have the mental stamina to be around people for long periods of time. Once of the reasons I would attracted to computer programming, even when working in a "team" you work alone for large periods of time.
To be clear I am not really a introvert or rather I am both an introvert and an extrovert when the situation requires it, I can carry a conversion, I can be "the life the room" but I find it mentally draining and exhausting to the point where if I am at a conference for example, I need a few days completely alone after to decompress.
So sure I sometimes regret that was not born with the mental gift of being able form these close continual bonds with people... but at the same time I dont have the desire to change that element of myself... if that makes any sense at all.