Maeve Binchy book title with Maud and Simon's story

Does anyone know which Maeve Binchy book has Maud and Simon's story? I've tried her website (not much info there) and I've tried reading reviews. The twins show up in Scarlet Feather and the new one Minding Frankie. I was hoping to go back and read their story. I'm pretty sure there is one.

Maud and Simon are twins who are neglected by their parents. They ultimately end up living with Muttie Scarlet and his wife.

Scarlet Feather is where you are introduced to them, and where you discover how they come to be a part of the Scarlet family. There is no book devoted to Maud and Simon, but they do figure rather prominently in the novel. That's really it.

They do come back in Minding Frankie, much more grown up.

I might be mistaken - it's been a long time since I read any of these books - but don't Maud and Simon appear or have some connection with Evening Class?

Nope; if I remember correctly, a couple of the characters from Evening Class may reappear in Scarlet Feather, and a bunch of characters from both reappear later in Quentins (absolutely lovely, by the way), and Maud and Simon MAY show up there (haven't re-read in a while), but their real backstory is in Scarlet Feather.

Simon and Maud are also in Heart and Soul - they go to Greece and stay with Vonni who is a character from one of the earlier books too - can't remember which one. I'm going to have to go back and reread all of these now!

Nights of Rain and Stars was the one in Greece were we first met Vonni.
I forgot that Maud and Simon were in Heart and Soul