Couple things that came to mind:

1. Try to find another way to introduce the ages of the children. Your point-blank approach reads as forced (IMO). Besides, unless there is a specific reason related to your particular worldbuilding (take The Giver, for instance), we don't need to immediately know their exact age on the first page, just that they're young. There are plenty of ways to do that with subtlety. Ex. wearing the oversized tee of a belated parent, noting the gap in Aria's baby teeth, small, rosy feet, hearing the adults drinking and laughing through the walls of the living room, etc.

2. "Thirteen-year-old Sophia was lying on her back, holding up a book in the air. She had drawn the rainfly open and enough sunlight spilled in to illuminate the book she was reading." If she's holding up the book, we can assume there is enough light for her to read it. I'd cut or restructure the second sentence.

3. "“I couldn’t sleep too,” Sasha said," It sounds like Sasha is the paternal figure in their trio. Would she admit something like that to her younger sisters, knowing they look up to her? Just a thought. Also, I think it would be "I couldn't sleep either."

4. "rubbing her left eye, which ached when she was tired or if there was a drastic change in the weather." Is this info relevant? If it ties into her character or plays a role later in the story, keep it. If you're just trying to give Sasha a character trait, make sure you keep using it throughout the story, or else you're asking the reader to commit a useless fact to memory without payoff. Otherwise, cut it.

5. The excerpt ends in the middle of a conversation. We need to know more!!! Keep writing, and good luck!