On Friends How Is Phoebe Related?

I know she is not genetically related and she was Monica's room mate but does it ever say how anyone met her? And if so, does it say who she met first? I wanna know cause' well, Monica is Ross' sister, Rachel was her best friend in high school, Chandler was Ross' best friend in college, and Joey came into the picture when he moved in with Chandler in the first couple episodes, Phoebe was there from the beginning, but it never says how she met them! If anyone could help that'd be great, its really bugging me!!!

Phoebe became Monica's roommate by answering a roommate ad Monica had placed in the paper, she was homeless up until that point. That was how she became a member of the group.

i don't believe it was ever really explained how Monica and Phoebe would end up as friends....Monica was supposed to have been sub-letting her Grandma's Rent Controlled Apartment and Phoebe was supposed to have been living with her Grandma and then suddenly in a few episodes it's said that Phoebe actually originally shared the apartment with Monica and was slowly moving out (without telling Monica) which left the room open for Rachel when she showed up.....basically, the "flash back" episodes and the actual very first episodes don't really mesh....BUT it's fantasy, i don't think Phoebe and Monica would have been friends in real life.

Joey is always in it (they've all done 238 episodes), he doesn't move in in the first couple of episodes, that's actually a flashback, a different episode - Season 3, Episode 6: The One with the Flashback.
The very first episode is where Rachel moves in with monica and Phoebe moves out.
Phoebe was Monica's room-mate just like Joey was Chandler's room-mate they are of no relation.