Conversation so far:
who is in prison in gossip girl season 4?
Ben Donovan is in prison in gossip girl season 4
what led to imprisonment for Ben Donovan in Gossip Girl Season 4?
Lily has Ben charged with transporting a minor across state lines and statutory rape, and was told that Serena signed an avidavit confirming that he did so.

Question: what was the relationship with serena?
Self-contained rewrite: what was the relationship with Ben Donavan and Serena in Gossip Girl?