What is lineage and what is its significant role in the epic in Beowulf?

Lineage is significant because Beowulf was written during
a time when most stories were passed on orally.  Only the most essential religious, and
some court/royal, documents were committed to writing. So, to preserve the history of a
kingdom or a tribe, the stories had to often use an elaborate way of telling the
stories: a way that is both entertaining as well as a record keeping.  When you hear
texts (think Biblical and other epics such as The Illiad), there are often long passages
chronicling "son of so and so, who begat this person, who reigned for a week," and so
on.  Also, story-telling was not just a source of entertainment and historical record;
it was a way to immortalize kings (in this world) and the heroic deeds done during their
reign. There is a theme of loyalty to the king/lord in Beowulf, but also amongst the
kingdoms during the time this epic was written.  So, those stories would often include
homages to the king, (beotword) and to preserve the identity of the king himself, the
story tellers had to repeat the lineage and therefore, lineages simply became part of
the style of this type of literature.  Very characteristic of 'epic
literature.'