Would it be weird to add his friend on Facebook?

[nbtts]

I have been doing casual with this guy for awhile his friends know me. I have one of his girl-friend as my friend on Facebook . Last weekend I hung out with lots of hia flatmates. I've net then quite several time but didn't really have a chance to talk much until last weekend. I like hanging out with them. They are fun. I enjoyed having a conversation with one of his flatmate. Wondering would it be weird for him if I add hia flatmate on Facebook ? I don't want him to think like i want to get too much in to his friend circle or something. But tbh he's not hiding whatever happen with me with any of his friends though.

[Maisie]

If you are friends with him i don't think there should be any reason to not be Facebook friends