To elaborate on my previous list, I have theorized on other characteristics on the Boss:
*Parents: Deceased or Missing or Abusive
Parents are a a fundamental building block in a child's life. More than likely, his parents were good parents. If the Boss had good parents, it is very unlikely that he would do violent things and start up an org. This is why his parents are probably deceased or missing. If they died in an accident early in his life, this would support his apparently violent and cruel nature as well as his theorized plan of eternal life and/or reviving the dead. If his plan succeeds, it's more than likely he wants to revive his parents. If his parents were abusive, then that would also support his violent nature, but would leave a hole in the explanation for his true motive (which we assume is immortality or reviving the dead).
*Siblings: None, and if any, are deceased or lost contact
Siblings help form good relations and love. It is apparent the BO Boss has very little love, if any at all. This wouldn't be very likely if the Boss had siblings. I'm assuming that he had none, and if he did, they are already dead (supports revival of the dead theory) or he lost contact with them many years in the past.
*Spouse: None
Other than the Boss's apparent attraction to Vermouth, it appears he has no feelings for any other person. Vermouth is the Boss's "favorite", and it is not likely you would describe any spouse as your "favorite', even if you've had previous marriages in the past. I am assuming and theorizing that the Boss has had sexual relationships with many women before, and probably considers Vermouth his "favorite" in that sense. It is highly unlikely that a man like the BO Boss who has had sexual relationships with multiple women in the past would have a wife.
These are just my theories, and I know they aren't that strong, but they're just my thoughts on it.