According to this report on Isaac Hanson--of the brothers/band Hanson--undergoing surgery for venous thoracic outlet syndrome, he is 26 years old.
According to me, bull crap. 26-year-olds don't develop venous thoracic outlet syndrome. This was Hanson's (Isaac, not the whole band) second surgery necessitated by a blood clot, and he's already got a third procedure to have a rib removed in the interest of opening up a vein on the books.
If Isaac Hanson is anything under 40, you can name more than one Hanson song off the top of your head.