Lineage-a group that can prove common decent from an ancestor.
Clan-claims it but can’t demonstrate it (IE the 12 Tribes of Israel).
Unilineal traces the descent through both the patriline and the matriline and the only way to be attached to this lineage is to be born into it, and consequently the only way out, is to die. This can be seen in the blood lines of the Tudors, whereas the only way to add to the direct line of the lineage is to bear children. The end of the line, however, is when the last of the lineage dies, therefore not passing his or her blood line to the next generation. In any case, a person with one such lineage will state the same line of persons every time. Everyone is related in some sense.
Read the entire article Difference Between Unilineal and Bilineal Descent for Size of Groups in a Culture via Ancient Digger at Socyberty