It was first in high school when I realized that being related to someone doesn't necessarily mean anything. I was dealing with my father's absence and this view worried some peers and instructors, but they understood when what was going on became clear.
As time went by and I went off to college and, now, I graduated, my view shifted slightly. There's a difference between disconnecting from someone who's left and disconnecting from someone who's clinging to you. I don't have to put up with someone who wants me to be miserable, wants me to serve her, and who doesn't take responsibility for her 50% of the relationship. I shouldn't have to be miserable in order to placate her (although I doubt even that would be enough for her).
Being blood-tied with my wonderful family does strengthen our bonds, but it doesn't obligate anyone to do something I don't want to do. I prioritize my family when they respect me; someone who disrespects me can't expect blood-ties to be enough for me to overlook it.
To see my loving family grieve over a departed cousin and then to be told by a senseless relative that she "grieves as though my daughter as died" is too much.