You are right Marked Ox. But the number of cases of such an occurance is small.
Anybody else interested in their family line, don't let that comment put you off delving back into your family line, it can be very interesting.
And Marked Ox, in my family I found a couple of naughties in my tree, including my grandad and grandma getting married only when she was 6 months pregnant. And yet she was a real snob.
Looking at your family tree is great. Did it myself and could trace it back down 1 branch to the 1700s as well as finding some interesting documents to read and some shenanigans.
The drawbacks on the genetics tests though are apparent but not considered by many I reckon. As well as what I've mentioned, I wouldn't want to give a US private corporation (or any other country) my genetics when you think of the data selling scandal with Facebook etc.