Question: I need you to settle an argument between my sister and me. My sister says that the only TV shows after Patty Duke that had twins were Full House and Sister, Sister. Who's right? A new outfit is riding on this.
Answer: Get ready to pick out something darling, Denice. Your sis is wrong.
I have to assume you mean shows with twin characters rather than actors, since Ms. Duke played both Patty and Cathy on her show (identical cousins rather than twins, actually). I'll also assume you mean identical twins, which rules out, say, Willie and Mark on The Hogan Family or Brenda and Brandon Walsh on Beverly Hills, 90210. But even ruling those others out, you still win this one.
Right off the top of my head, you need only tell (or remind) her about the Barone twins (Everybody Loves Raymond) or the Burke twins (Two of a Kind, another Olsen twin comedy). I'm sure there must be more I'm forgetting.