Irving used to live in the grotto (at least that's what conclude). When he was utilized in a mission for Alexander and Selina they decided to keep him with them to be of further assistance. So metaphorically. Like when Alexander had to give Irving up to the Automatons because the Scarlet Man said to, Alexander obeyed, even though he didn't want to give Irving up. And even though Irving didn't want to go he still obeyed. Great example of the story of Abraham being told to sacrifice Issac up on the mountain. And of course their original "son" Ishaan the little robot represents Abraham and Hagar's son, Abraham's first born, Ishmael.
So on and so forth. That is yet another feature of this game that makes it ROCK!!! Seeing all of the stories unfold is so cool. Me and my son are constantly saying, "Oh this is like this part in the Bible, oh and this is like that part in the Bible!"