Start with high-confidence ya blended family stories books, then narrow by subgenre or adjacent topics.
Camilla
Ann Marie Lee, Madeleine L'Engle
And Both Were Young
Madeleine L'Engle, Léna Roy
The Ruby Notebook
Laura Resau
Me, Penelope
Lisa Jahn-Clough
Wonderful Feels Like This
Sara Lövestam
If Only
Richard Paul Evans
Guitar Notes
Mary Amato
Last Chance Joey
Meredith Resce
Things to See in Arizona
Mary Vensel White