Couple #1 was having marriage problems and thought buying a home and living together would help.

I had this hunch based on a couple of empirical observations. Interesting to see another data point. I think some wives in difficult marriages grasp at homebuying (or having a baby) as a cementing factor. Looks like it usually fails (and if anything, contributes to accelerating the fracture). On the other hand, I have also observed some good marriages fall apart after buying an unaffordable home and the resulting financial distress from it.

I think the correlation between housing bubble and its impact on marriages would make a fine subject for a few Ph. Ds in Sociology!