My brother just pointed out that Harry Patch, the WWI Veteran who died last month was in the Duke of Cornwall's Light Infantry, and wondered if we had any connections to that regiment. A quick check of my notes shows that our grandfather (mother's father) was in that regiment, and possibly both his brothers. I'm sure about my grandfather, since he had a fairly distinct combination of first name and initial. His two brothers are likely to have been in the same regiment, but using the Medal Rolls I've never been fully confident that I've identified their exact records, since there are several possibilities with similar names.
My other grandfather was in the Canadian Expeditionary Force, which is a whole other story!