Pretty shortly after I got in to genealogy, and met relations previously unheard of, living quite far away, although quite closely related, and saw very strong family resemblaces, I came to the conclusion that, if you see someone, who looks very like someone else you know, then there is probably a damn good reason!
Take the mathematics involved in any average family increase over, say, five generations, and the last of the counted generations only has many hundreds, maybe thousands, of cousins. One can't possibly know them all. Add to this the illegitimacy factor, the swapped at birth, given away, or taken-in babies, (and here I am not referring to formal adoption, but of course, that also comes into the picture) and the genetic line is already kidding you.
Genealogy is fun, and I believe if one is in to it, then one should endeavour to keep to the right line where possible, i.e. checking available information at source, and not taking any published research as gospel, i.e. IGI, which is useful, but not infallible. But equally I think one has to be open-minded about it, and light-hearted too.
Before I started, I was fiercely Manx. Now I know that we are a real mish-mash of cultures, over a long period, and today, that process is being accelerated. S