That would be a son-in-law's sister. She never wanted kids of her own, even to this day (she's 48 now). I don't mind, as she's rich and showers my grandchildren (her nieces) with gifts. I don't get how anyone would not want kids, particularly a woman. But she's a career lawyer dedicated to her profession. And the only female among 5 kids having 4 brothers who have kids.
I never wanted children but love my nieces and nephew. I’m as happy as a clam.