E was Embraced by Lily, also a Thin Blood, who he had been seeing while in Santa Monica for a surf contest. Lily Embraced him one night but he didn't understand the severity of what she had done to him and he rejected her, but when Lily went missing E came to regret what he had done and wanted to find Lily. Unable to do so himself, he asks the fledgling to find her.
Even though Thin Bloods are known for not being able to Embrace, E was Sired by a thin blood. The Generation system might be an explanation for that: Lily, most likely, belongs to the 14th Generation, which is considered thin-blooded but still not the bottom of the hierarchy; Kindred of this generation can sire childer, but rarely manage to do it. E is 15th Generation, which is currently the absolute bottom of the heap; he cannot sire childer at all.
It's unknown whether or not E and Lily are still together in the modern nights, but in 2018 he was seen by Therese Voerman in the company of a pregnant mortal woman, and he claimed he was the father. He and the woman were being followed by someone in a black Tesla.