Both of my mom's parents on were named Fran (Francis and Frances), so that's the default middle name on that side of the family. By my count off the top of my head there are 6 of us, children, grandchildren, and great-grandchildren with a middle name of one or the other. I look forward to passing that on, if my wife will let me.
On the other side, David is kind of a family name. Its flipped back and forth between First and Middle Names for first born sons, so I expect the first boy I have will get that as a middle name, as well. Its a little easier name to swallow than Francis, too.
I like having family names, its an interesting reach into the past.