Azariah on Jun 14 2005, 10:12 PM, said:
The healing powers of the seventh son is also a superstition held in France, the seventh son was called a Marcou and branded with a fleur-de-lis (though i've also heard debate of whether it was the fleur-de-lis or the rose, since traditionally the sixth son is branded with the fleur-de-lis, and the the seventh is branded with a rose, but i don't know much about all that.)
I'm not sure of the origins of this myth though, but I don't think the origin is known either. hope that helped.
There was a village that abandoned every seventh son of a seventh son and a priest adopted all of them.