I googled that usher syndrome last night and if it is that it seems like they would both have the gene. It said there's a 25% chance for each child you have to get them both. There's different levels of the syndrome too. Any medical professionals please forgive my terminology lol because I'm not in the medical field at all. The different levels have to do with how deaf they were born. In his case he's profoundly deaf so he would be level 1. It says their eyesight gets progressively worse but doesn't start until they're older. It actually said 9 or 10 but also said it can start before that. They can get tunnel vision too because it can mess with the ability to see from the sides of your eyes. I forget what that's called. I want to say profile but that's not correct. Basically they have to turn their head left or right to see what's next to them. It also said something about weight gain. Please feel free to correct this lol. Like I said not in the medical field at all. Also this was a 2am falling asleep google.
Oh I'll add it did say cochlear ear implants are recommended and some use asl but if they loose their vision they tend to use tactile sign. Which I googled because I had no idea what tactile sign is and still don't really but it's sign based on touch??
So I hate to say this because I'm cringing as I write it but possibly they knew this all along and that's why they got the cochlear implants and big t didn't just impulsively do it.
Eta: lol I should have read all the comments before I commented my mini novel because I see the question was already answered now.