On The Partridge Family what was the name of best friend?

The Partridge Family didn't have a specific "best friend" character, but the closest thing would be Danny Bonaduce who played Danny Partridge.

While Danny was a member of the family, he was often depicted as a close confidant to his older sister, Laurie Partridge (played by Susan Dey). They shared many adventures and often confided in each other.