I suppose it's possible, but it seems odd to me. Please clarify. Perhaps John is a middle name for the brother? I noticed this because a merge notification came up wanting to merge the 2 Johns. I ignored it. But until the brother John has something distinguishing him from the Senator, this will keep being an issue (merge requests), unless, of course, this is an error entirely.
According to http://en.wikipedia.org/wiki/John_Kerry
He has three siblings: two sisters, Diana (born in 1947) and Margerie (aka Peggy; born in 1941), and a brother, Cameron (born in 1950)
So there are another two sisters who could be added too