Check out with your Doctor as the Meds can cause this we get posts saying the same thing ,
I don't think it's a "fluke" that both your boys have tics. I think it's shared genetics.
My family is similar to yours. I also have three children, the oldest and youngest affected by tics, and the middle (son) not. My oldest was put on Ritalin for elementary school. He had tics, and they stopped when he was taken off Ritalin. My youngest son never was put on any medication, he has tics that come and go. My middle child (a son) has no tics, and no ADHD.
Best wishes.