I also have 3 sisters, which none present any "issues"
I have CM and SM, as well as scoliosis. I have an aunt currently being tested for CM. I have 3 children, 2 with symptoms of CM but not tested. All of my children have mild scoliosis, as do my siblings.
I actually suspect my.mother has it but she wont go get checked lol she doesnt like doctors.. but the symptoms she tells me just mirror my own
My sister and I both have Chiari and we suspect that my sister's daughter probably has it too. I also think that our father probably has undiagnosed Chiari -- he has complained of headaches lasting several weeks for as long as I can remember, and has always had neck pressure/pain too.
I know that my grandfather had "water on his brain" and had a shunt. I do not know if he had ever been diagnosed with chiari. I have chiari and syringomyelia. I think that one of my children probably has chiari but I have not had them tested.