I'm sure the twins will have their moments, but they're well on the way to recovery mentally. Right now their hands are not nimble enough for sign language. Picture them as if they're gripping invisible handle bars. They can't extend their fingers.
Vann is going to be a tricky subject. As far as we know he's not aware Caleb is his biological dad. I haven't gotten that far in my head.
Asa might pop up in the next story. Significant part? That remains to be seen. I'm still deciding.