It doesn't matter if your families have know each other. What matters is how you feel about it. The one guy who makes fun of him probably sees that you don't like this and that other guy could be your guy. Yes just let him deal with his own stuff. Otherwise he will become dependent on you for emotional stability. This is a friend. A non-friend would be dependent and lead him down a path of less independence and it would be a mistake.
well just show concern for him. you know, ask him how it's going and how he's feeling you know? give him a hug, but don't kiss him. let him know that if he needs to talk that you're there as a friend if he needs anything. :)