Being that Deimos was supposed to be around 20 when he went to prison, and was so in love with Helena, would be kind of hard for Xander to be Deimos' son. However, he could be the cousin/nephew who was very close to Deimos, and worked with him, unbeknownst to any family. Thus, he did whatever Deimos asked of him, was the one who contacted people, invested monies, had the secret bank accounts, etc. etc.