Re : Sarah Bee
Sarah, the situation postulated could _conceivably_ happen.
A man who knows he was abandoned at birth could meet another, older, man carrying a similar physical trait to him self. i.e. birthmark etc.
"Is this man my father?" says younger man.
"Is this man my son?" says older man.
Get a DNA check says the man in Boots.
See, a possible situation, as described, and no sexism whatsoever.