On a parallel line, I recently booked by wife and pre-school age child on QF29/30 MEL-LHR-MEL for February (same PNR) and when I later entered seat requests, it split them up, placing them several rows apart!

It took a call to get them placed together, and the excuse was that as one profile had 'aisle' and the other had 'window', the system tried to accommodate both profile requests. My wife and I have this window/aisle conflict in our profiles too (and have had for years), and have never been split up when flying together.

In this case there is a surname issue also: wife uses maiden name and child has double-barrelled version in mother-father surnames format.