His best friends request

So I have been hanging out with a guy for about 3-4 weeks now. Everything is great. I’ve spent the night twice, hung out a few times, met his best friend, and he’s said my name when talking to a friend on the phone. But his best friend I met once, just friend requested me. I don’t know how he found me, besides being mutual friends. What’s it mean when his best friend, friends requests you?