I am using FTM2008. I have three distant cousins using earlier versions of FTM for their own genealogy research. Another is using the online site geni.com.

Each of these cousins has research interests that only partly overlap with each other, and with mine. For instance, a cousin on my father's side doesn't care about my mother's ancestors; and likewise, they have ancestors that I don't care about.

At first, I had only one cousin doing research. He emailed me a GEDCOM file, and I merged it into FTM. But merging is tedious and error-prone. I still have little annoyances in my FTM file due to the merge that I did. I am not going to do that again, and it is clearly impractical, given that I have multiple cousins doing similar things.

I know there's no magic bullet, but does anyone have coping techniques for sharing data when there are multiple people doing similar research on overlapping sets of people?