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Alanis Morissette has a male twin. Can't think of any other famous females with a male twin offhand.
Don't humans twin at a rate of 1-in-100 or so? In that case your chance of having an opposite gender twin should be about half a percent.
> In that case your chance of having an opposite gender twin should be about half a percent.

Only if you assume half of all twins are opposite sex, which is wrong; that may be correct for fraternal twins (though since environment at conception seems to affect sex, maybe not), but it certainly isn't for identical twins which are always the same sex (by sex chromosomes, at least.)