My friend's boyfriend is suddenly talking to me?

[ArrogantArtist609]

Because he wants to be friendly to his girlfriend's friends. I highly doubt he has an alternate motive based on what you said. There are two groups of people you have to be on their good side when your a boyfriend.

Friends
Family

Friends even more because a lot of times girls don't give two shits what their parents think of their boyfriends. However, a girl's friends can manipulate how she reacts to certain situations and also having your girlfriends friend's on your side and friendly with you is good for big group outings. Its very important to be on good terms with your girl's friends so that is most likely why he is nice to you all the sudden.