I'm trying to change factions in g1 but the leaders tell me to renounce my claim to my old faction, how do i do that?
Also is it done in a simular manner for the rest of the series

I think you just try to join the new faction, and the old faction will probably turn against you. You have to make sure the views you've expressed on serviles match those of the faction you're joining, so you might need to have some more conversations or use a cheat code.

This is just for Geneforge 1, I haven't played the others.

Got it, I just had to do the takers join quest. Some times the game's dialog can be a little unclear what NPCs want.

I also know there is an sage in Peaceful Vale that can once per game make a faction like you regardless of your behavior so far. Exsmple start out getting in the good graces of the Awakened and Takers, the talk to the sage to ask about putting in a good word with the Obayers and boom, you can join that faction

That's good to know. I've read too that if your leadership is high enough you can talk your way out of doing the quest to join a faction. If you just did the Takers' join quest, you can't have made the Awakened very happy ;)