Or were any of the individual FF members apart of the Avengers?

I think at some point they've all been apart of the Avengers (if not an offset of the Avengers) or at the very least were honorary members to conquer a threat.

at least 10 members of the Fantastic 4 have been Avengers:

Thing, Mr.Fantastic, Invisible Woman, Ant-man, Spider-man, She-Hulk, Black Panther, Namor, Crystal, Storm

@oldnightcrawler: Hulk and wolverine too

You can say they are Fantastic Avengers. Plain and simple.

I wasn't going to count that/those versions of the Fantastic 4, but, yeah.

also, wasn't Luke Cage on the Fantastic 4, or am I getting that mixed up?

@oldnightcrawler: yup. He filled in when Ben lost his powers.

The Human Torch is the only one of the core Four to have never been an Avenger (To my knowledge).