Although many don't marry, they do live as couples and fathers are mentioned on birth certificates, so I doubt it will be a nightmare.......
Well, whilst not wanting to pre-judge, it's certainly not unusual these days to find women with 3 or more children, all with different fathers ! At least with Victorian genealogy, when you found the father of one, you usually could put his name to all of them (well, on paper, anyway

). I'm sure genealogists in 100 years time will have as many challenges as we do, but just different ones. I suppose living in a nanny state with "big brother" recording our every move will benefit someone, even if it is in 100 years time !
