I sometimes wonder if the extreme VS streak amongst these family members may be related to the significant writing challenges they also share, a la Silverman: trouble changing visual all-at-once-thoughts into a linear sequence of words. Don't know how this could be tested, though - Silverman's a bit skimpy on that part!
I don't know about your family or anyone else MichelleC, but I can tell you that my ds who struggles tremendously with writing challenges is also extremely VS.
squishys, my ds is extremely good at and also very interested in engineering-type design and modeling, also very good at math (but not as passionate about it lol, and was not a fan of show-your-work in early math). He's always been light years ahead of grade level in reading (or was back when school measured reading comprehension etc), but is not terribly fond of subjects in school that require a lot of reading and rote recall from reading. He learns by doing, handling things, and visualizing in his head.
polarbear