Grevious is NOT a droid

As only a few may know Grievous is a cyborg not a droid.

He is from the Planet Kalee home to his species the Kaleesh

His hate for the Jedi first began during the Huk War when the Jedi supported the giant mantis like creatures known as the huks who wished to enslave his people.

On a shuttle to one of his campaigns, Qymaen jai sheelal (Grievous) was shot down and the shuttle crashed on a semi-aquatic campaign, surviving Count Dooku finds him and tells him the Jedi shot him down. (Even Though the separatist shot him down on sidous orders due to the fact he could be a good "asset")