Subject zero is Aileen Bock and she was a scientist heading a surrogate program which was her using the genetics's of her unborn child to access his/her genetic memory. This surrogate program is basically competing with Vidic's Animus project. Because the genetic memories aren't her own they can only record for a few minutes. The tapes are from secret recordings Vidic made using bugs in the early 80's to spy on his competition and boss. In discovering that her ex husband is an ancestor of someone they believe to know the whereabouts of a piece of Eden, Warren Vidic convinces him to sign up for the animus project along with his son. After Aillen's technical wiz goes off to work with Vidic for a while he comes back apparently with a way to make the surrogate memories last longer, but his ends up going horribly wrong. They said then that she had to retire prematurely because of the accident, but there and implications that she died as a result of the accident. Maybe not, maybe we will meet Aillen Bock in a future game and she will help the Assassin's this time.
What we do know is that her ex husband and son became involved in the animus project therefore both would represent a subject between subject 2-15, even possibly 3-15 as Warren tells Ailleen he will will be doing the experiments on himself after an undiagnosed epileptic dies during a stint in the animus.