Jason and Alyssa are both vampires that meet in the 19th century. Upon meeting, they don't know that they both previously were part of the same vampire group, The Millers. When Alyssa mentions she is part of the group, Jason is a bit shocked because she has by this point become friends with the Dawsons. But he is even more shocked when he finds out her mother is May Miller, his former girlfriend. Their friendship shifts and they have their distance for a few years, untill meeting again in a pub and deciding that they would not let May get in the way of their friendship.
However, Jason keeps wondering who Alyssa's father is, as he was aware of the affair between his former girlfriend and his brother. Internally he still has some doubts. He goes on a discovery trip to find out the details of May's fertility, and comes to the conclusion that Jared is the father. Jason finds his brother and asks him, to which Jared replies with a witty comment confirming Jason's theory. Jason doesn't mention to him that he and Alyssa are close friends, he just asks for his relationship with May and if he was aware of her fertility.
In the meantime, Alyssa is on the hunt for her father herself. In an attempt to find out, she returns to her mother several times to get information. But May has kept her pregnancy mostly under wraps, and the few who did know she was pregnant, never lived long enough to calculate back to the conception of Alyssa. Alyssa's quick grow rate has kept those who saw her growing up wondering when she was born exactly.
Seeing as the Miller Compound doesn't give her answers, Alyssa returns to her friends. Around the end of the 20th century Jason choses to not tell Alyssa their connection. Alyssa continues her search and occasionally returns back to track down a lead, but is mostly unsuccesfull. Jason later admits to her he has not always cooperated in her search for her father, saying that he once of twice got rid of any leads in fear of loosing their friendship. When Alyssa eventually does find out that a certain Jared is her father, Jason confesses everything he knows and from there on the two are aware that they are in fact uncle and niece.
When Alyssa goes to confront her mother about it some time later, May doesn't confirm nor denies it, but subtly hints that Jason was intended to be the father all along. Alyssa gets mad for not getting questions, and asks her mother when she will ever be worthy of her time. May replies with 'never' and Alyssa returns to Jason who comforts her. May has Alyssa followed back, and starts to investigate on Jason and the Dawsons.