If you’re at a pub quiz and someone asks “How many Nolan Sisters have died?” the answer is two. Say it with confidence. Then buy the next round.
If you want to be really smart, add: “But their mother, Maureen Nolan Sr., is still alive at 94! She’s the real survivor.” Yeah, that’ll impress people.
So, to answer your original question: two. And we miss them. But the other four are still out there, singing “Don’t Make Waves” and probably arguing about who gets the last biscuit.
Now go enjoy a dance. They’d want that.