Interesting study. I am always so skeptical of these types of studies. Would be curious to see if this accounts for "cross-cultural" couples as well. My boyfriend and I met and fell in love in graduate school. Him, being from one of the most conservative cultures in the world (hailing from South India), and me a free-spirit from California. I'm positive our mothers' supportive/nurturing ways took on different meanings and had less to do with us falling in love and making it work and being able to formulate lasting commitment than current circumstances and the "inexplicable" factor you mentioned above about why two people fall in love.