I cannot believe I'm talking about reproduction in a Disney video game forum...Now that intrigues the hell out of me as a nursing student. I never considered chromosomal disorders, nor did I know that some sperm have two chromosomes.
Yes, some sperm have double chromosomes, or duds, and usually the resulting child themselves will have chromosomal defects. Eggs will always have an X-chromosome, so I've read, because a chromosome-less egg simply isn't viable, but I could be wrong and they discovered something new. Some sex chromosome defects include
XO - Turner syndrome, has the appearance and body of a female, infertile.
XXX - trisomy, female, abnormal physical development, mental underdevelopment, emotional underdevelopment, fertile.
XXY- Klinefelter syndrome, underdeveloped sex organs, small testes, androgynous to feminine in appearance, male, infertile.
XYY - quite possibly the most normal, increased physical development, learning difficulties, not more aggressive than normal males, VERY fertile.
There's more, but listing them all down would take a lot of work.
Since they came from the same oocyte, true opposite sex identical twins are incredibly rare, much more those who are normal and healthy. The exception is "Polar twins," in which a single egg divides in two, and then is fertilized by two different sperm, but I don't think they can be called identical out of technicality. They share the same blueprint by half, at least.
Oh my lord above, we’re still talking about this. One day, Jesus Christ will descend from the heavens and the first thing he’ll be asked is, “Do you think Roxas/Namine & Roxas/Xion are incestuous?”
How do you think I feel? I brought it up to emphasize the semantics, but it's getting ridiculous.