Familial Bond

Maybe to explain it with a bit more words:

A vampire must attempt to block to play intercept. So, C attempts to block and can play Familial Bond. The text of Familial Bond gives intercept, and apart from that references "If this block fails". So it will happen, if you do not have enough intercept (or are forced not to block e.g. with Elder Impersonation) - it doesn't matter that you never had enough intercept to catch the acting vampire, that is something the game doesn't keep track of. And nothing the card asks for. What's important is that you played the card, and didn't block successfully.