I think it was mentioned on the show that she is related to the family on Maurice's side. Then who were Serena's parents? Were one of her parents Maurice's siblings?

Anybody know for sure how Serena is related to the family other than being Samantha's cousin?

All I know is that Serena was Sam's cousin and came from Maurice's side of the family. I don't know any other details, but then Bewitched was always iffy on those kinds of details.

I always felt that she was Maurice's neice. Samantha and Serena are identical cousins like Patty and Cathy on The Patty Duke Show, and Cathy was from the fathers side of the family. I guess thats not a reason to conclude this but thats the way I perceive it.

I loved Serena, they could have done given her her own show.

In the episode Samantha's Hot Bed Warmer, Serena calls Endorra "auntie Endorra". Now was she being sarcastic or is Serena on Endorra's side of the family? That would be that Endorra has another sibling.

No, if Sam and Serena are cousins that means Maurice and Endora would be her Aunt and Uncle.

No, if Sam and Serena are cousins that means Maurice and Endora would be her Aunt and Uncle.
That's right..."Auntie" Endora would've been Serena's aunt by marriage, since Endora and Maurice never made their split official - or final!! :D