John,
Do you find it a little strange that the Horn daughter's middle name would be the same as the father? Was that a common practice? What I've usually noticed is that middle names like that would come from a sibling or aunt/uncle, rather than the parent. Maybe it's not unusual and I'm reading too much into it.
I keep hoping I'll stumble across the Horn family somewhere and this will resolve itself rather quickly.
Thanks for all of your help!