Idea from @brackenfur and this post as well
The three being raised by Firesand. I love this idea so many reasons because my goodness are family bonds just cardboard for the most part.
But I have two other ideas.
1. Firestar raises them as a single dad
So basic thing is that Sandstorm was taken by twolegs.
Firestar finds out and questions them she they didn't go to him. Leafpool expresses her frustration. He's Firestar, how could she tell him? How he's so distant that he didn't realize she'd fallen in love with Crowfeather. That sometimes she's surprised if he sees her as just her. How she wishes he had just been her father, not firestar, just her father.
This makes Firestar reflect deeply and guilt sets in. He failed his children but he will do his best to do right by them, to help them like he should've. He offers to take the kits. Firestar even leaves for a few days before LeafSquirrel comes back.
He returns to camp with kittens in his mouth and the clan questioning what is happening. Firestar only says their his kits and asks Ferncloud to nurse them which she agrees.
Hollykit and Jaykit are already named but he gets to name Lionkit.
He refuses to sleep in the leaders den and sleeps in the nursery til the three are apprenticed. Firestar does more self-reflection regarding Jaypaw’s blindness and thinks of how he viewed Cinderpelt’s injury. He saw her living as a tragedy instead of the happiness she found. He won't do the same to his son.
The clan doubts his youngest son, he won't. He makes himself Jaypaw's mentor. Bias be damned.
Sandstorm comes back and is stunned when she meets the three and vice versa.
2. Firesand actually had a second litter when they take in the three.
Similar thing from the previous idea with Firestar's reflection and wanting to do better at being a parent.
Firesand had another kit: Antkit. Despite their tragedies, the clan thinks they're blessed with such big litters.
Lionkit and Antkit form a rivalry with Berrypaw and Berrypaw has two deal with two bulky kits snapping at his heels.
Siblings' shenanigans and the expectations of being firechildren ensue. Finding out about the prophecy makes them question (all the more interesting since Dove is still the third).
These ideas mostly stemmed from this image in my brain of when Hollyleaf exposes the secret.
Firestar tries to reason with her, placing a paw on her shoulder. Hollyleaf responds negatively and strikes Firestar. He loses his balance and falls from the tree.
A sickening crack hits the clearing just as hard as the ginger leader did with the tree roots. The medicine cats rush over to help but everything slows down for Hollyleaf.
Hollyleaf is horrified, and runs, and her brothers run after her.
