A condition whereby one has
incestuous feelings towards one's sister. Mostly prevelant in areas where there is a high
preponderance of ginger haired people with webbed feet and one eye
in the middle of the forehead (e.g Bedford or Luton!)
Stanley "Dad! I fancy our Mable, does that make meincesbian?"
Dad: "No my little slack jawed, banjo
playing, bedfordian offspring, it just means you have adelphepothia, same as
your mother and
her brother before her."