I can think of a lot of book series that that feature fictional families.
It’s a tried and true trope in children’s fiction, from Arthur Ransome’s twelve-book Swallows and Amazons series (featuring two sets of siblings), to CS Lewis’s Narnia, and Enid Blyton’s long-running Famous Five series.
Christian fiction has a lot of series centred around siblings.
Many romance trilogies feature three siblings (which always leaves me pitying their poor parents, having to pay for three weddings in close succession). There are also the family saga-type series, such as Karen Kingsbury’s Baxter Family.
The family series I have most read and reread has to be Janette Oke’s Love Comes Softly series.
These eight books covered the love story of Clarke and Marty, then moved through time to show the romances of many of their children. I read and enjoyed all the stories, although I think my favourites were the first three stories, and the last.
Oke then moved to the next generation and wrote the four-book Prairie Legacy series about Virginia, one of Clark and Marty’s many grandchildren. The series ended with a note from the author to say she couldn’t write any more books because that would mean Clark and Marty having to die of old age, but she knew her readers wouldn’t like that. It’s an advantage of fiction: the characters can live on in our minds for decades longer than the lifespan of a real person.
The reason I like these stories is a testament to Janette Oke’s storytelling ability, but also the way she was able to weave in deeper spiritual truths and the importance of trusting God even when things look impossible. That’s why they’re my favourite fictional family.