"Its a wise bairn that kens his ain faither!" 
Skoosh...
That's a saying I came across many moons ago & it's true in quite a few cases as has been seen here & on other sites.
I thought I'd point out something
'unique' for the benefit of others who may find something similar...
If ever I had any doubt (I don't) of who my biological father was, I have the ultimate proof!...
I (a female) have the exact same birth mark, in the exact same location as my 'dad' & it wasn't painted on

For me, that would have been 'solid' proof, not that I had any doubt, prior to doing a DNA test to find another relative & in the process, I have very close (confirmed by paper trails) matches to my father' relations.
Annie