Gossip Girl Question! Lily and Rufus?

[someoneeeet:]

okayy its about season 1 (i know, im so behind) ; how does serena's mom lily know dan's dad rufus? what history do they share?

i need an answer & i need it fast!

please and thank youu O
does serena know about her mom's past with rufus? or does dan know?

 

[Scarlett2079]

they went out together in the past! (and get back together again later on )