It really is a small world, isn't it?
On The Vampire Diaries Season 6 Episode 4, a very strong installment of this CW series, we learned that seemingly everyone in Mystic Falls in connected.
Sarah's mother was a woman named Gail. She was pregnant with Zach Salvatore's child.
We learned this via a flashback to 1994 that Kai prompted Damon to relive because a certain incident took place on May 10 of that year; the same date on which Kai, Bonnie and Damon are now stuck.
See, Damon had just returned to Mystic Falls and Stefan was willing to give him another chance... only he then took Damon's daylight ring and locked him away after he found out that Damon was feeding on Gail and Zach.