I just stumbled across this, not sure if it's been posted yet (?), but near the end of the video Dr. Daniel Peterson says that "in general there has not been a strong association" in patients w/XMRV & the percentage of children and spouses. (paraphrasing)
http://www.youtube.com/watch?v=7B5kghQL3x0
http://www.youtube.com/watch?v=7B5kghQL3x0