you were a stand user that was mind controlled by one of Dio's flesh buds after removing the flesh bud, Jotaro introduced you to the team

Jotaro: I say we bring this person with us.

Kakyoin: A new member, hmm? They do certainly look strong.

Joseph: It just makes me wonder how many more people we can save from Dio's control.

Polnareff: In any case, let's give this new member a very warm welcome!

Iggy: eating a bone, ignoring everybody

Avdol: What's your name, new member?