I've got a grammar question, in the sentence "I heard my boyfriends friends band play music live", where do the apostrophe's in "boyfriends" and "friends" belong?

Here's a link with a definitive answer:

http://www.grammarbook.com/punctuation/apostro.asp

And an interesting situation:

a band plays live music.

boyfriend's---assuming you only have one boyfriend.

And is it one friend or friends to begin with?

Don't deal with my "situation."

Just go to the link and decide from what you see there and then just be consistent in the future when you use the possessive case.