I won't argue with that.

[But on to the main point--which he can and will argue with.]

So what if he's weird?

Look, we were family before, right? Don't you think any kid who winds up in a crazy place like this is gonna miss his family? All we have to do is be around for him and look after him.

[Make sure he knows how to use a weapon, keep him from being eaten by monsters. Family stuff.]