What's the Name of That Book??? discussion

I think this book was written in the 1960s or so. The author was definitely famous for her gothic/romance books, except I can't remember who it was.

The plotline features three children - John, Marci or Marcy, and Kit. Marcy is depicted as bold and fearless, Kit a bit more colorless, and I don't remember John very well, but he was much nicer to Kit than Marcy was.

The major events included (view spoiler)[

Kit tries to join in their play, is upset that she is excluded, and falls down the stairs, injuring herself for life.

Kit somehow gets John to marry her, but they aren't happy.

Marcy/Marci dies in a car accident and John goes off to war. It's indicated that he plans to die in battle.

(hide spoiler)]

I think it has the word "peppers" in the title.

Can anyone help me remember this crazy book? Many thanks!

I think I found it: Two Little Children and How They Grew?

YES! That's it! Thank you so much, Ayshe!

Who wrote the book

Doris Miles Disney