Do you think there`s a reason why Gossip Girl`s 1x08 is called "Seventeen Candles" and The Vampire Diaries` 1x08 is called "162 Candles"?

TVD called 1x08 '162 Candles' because Stefan became 162 years old and Gossip Girl's 1x08 was called 'Seventeen Candles' because Blair became 17. But I don't think there's neither a connection between the two nor a purpose. I think it's just a coincidence that the two episodes are both episode 8.

I dont think they did it on purpose

Only representing how old each character became, not related in any way.