Bloodlines are essentially families within the tribe. They are used to identify other members of that bloodline or another. Some families may rival against each other or clash in the pack; others are secondary families that get along well with others. Each bloodline has at least one distinct trait [whether physical, mental or emotional] and the gene is passed down. The 'head' of a family is the leader-- and if that family is restricted from adopting others, you must ask them for permission; heirs are the next in line to be the head, should something happen to the leader.
OPEN - This bloodline is openly accepting new family members.
RESTRICTED - This bloodline has a requirement; speak to the leader to join.
CLOSED - This bloodline is no longer accepting new family members.