Yes, in regards to World War I, I remember hearing or reading in the family history book, that my grandtather's brother served in that war, and died there, and is buried there in Europe, in I do not remember whether Flanders field or one of those places. So we already did our part for World War I, no need to add to that now.
On my Dad's side, my great-grandfather did not serve in World War I due to an eye conditions, his registration card notes something about weak eyes, and also he was about 40 years old, a minister and a family man with several children to feed, and also he was living in China during part of that time, so I suppose that he can be justifiably excused. Needless to say.