Board Thread:Episode Discussions/@comment-1181222-20180131111324/@comment-1458758-20180201174445

How is it that this was established back with Haku, confirmed again with Yamato, but people still don't get how Bloodlines work?

Ninja clans have hidden techniques, which is why you'll basically never see anyone who isn't a Nara using Shadow Sewing, or a non-Akimichi use Multisize, because the clans guard those techniques as literal military secrets. Bloodlines are abilities that are much the same, restricted to a clan, but also have the weakness that its a genetic element. So by kidnapping a Bloodline user, or even just removing the organ responsible (Kakashi/Ao), one can make use of this for themselves.

So while not all users of a bloodline are from the same clan, you can basically guarantee they share an ancestor somewhere up the line.