Twins' kids

Is it true that if one identical twin has a child, there is a 100% probability that the first child from the other twin will be the same sex? My identical twin brothers are always telling me this, and like everything else they say I don’t believe them. Neither of them are married nor do they have any children.

Well, I know a set of twins. One has two boys and the other has two girls. So there goes your 100%. I would imagine that the sex of twins offspring is the same crapshoot as anyone else’s, unless there are genetic conditions that affect the proportion or viability of sperm for each sex.

Sounds like they’re pulling your leg. I can’t think of any reason the children of twins would have a greater probability of being the same gender than the children of non-twins.

Now I have further clarification from my twin brothers (watching over my shoulder, as there is now money on this):

Twin A has not previously had any children and gets someone pregnant - she has the child.

Twin B has not previously had any children and gets someone pregnant - there’s no chance the child will be of a different sex than Twin A’s.

Their response to cher3’s twin friends with different kids is that they weren’t in the same sequence - IOW, one twin had kids once before, there was an aborted / unknown pregnancy <?>.

At any rate, I’d love to shut them up on this once and for all. (And recoup my loss for taking the under yesterday). Any geneticists out there?

If you had been paying attention in 7th grade health class you would have learned that the sex of a baby is determined by whether the lucky sperm cell carries an X chromosome or a Y chromosome. Human males, including twins, produce roughly equal numbers of X-carrying and Y-carrying sperm throughout their lives, which are mixed together all at random. Now, do you honestly think that Twin B’s balls are somehow going to “know” the sex of Twin A’s baby and that Twin B’s balls are only going to produce that kind of sperm until Twin B fathers a child and that that information is somehow going to then be transmitted back to Twin B’s balls, which will then start making both kinds of sperm again? Do you really believe that? Or do you think it’s more likely that your brothers are jerking your chain?

wow, it’s like a weird combo of the EPR and the Twin Paradoxes. kuh-razy…


Actually, since they bet me, they’re really jerking their own chains now. They sincerely believed this, poor bastards. (Literally and figuratively).

Thanks everyone for their input.