From what I know it's about this:XX & XY are (usually) normalXXY (most common) canbe a wide variaty of things, from a fertila female to an (usually infertile) male.This is also the most common cause of hermaphroditae (medical term: intersexuality. The most common is iirc a infertile female and slighty less common an infertile male.XXX is always female, usually infertile.I've never heard of a (live-birth) XX(X)*(Y)*, but I don't think it's impossible. I'd think it's highly unlikely though, since it usually goes like this:X from mother + x/y from fatherAnd when it goes wrong it is usally this:X from mother + xy from fatherAnd it should be possible to (altough extremely rare I think):XX from mother + xy from fatherMore seems impossible to me if the mother and father are  healthy.