Third Type of Twinning – Semi-Identical Twins

The medical community has confirmed that in fact there is a third type of twins called half-identical twins, or semi-identical twins.

Genetically and conception wise semi-identical twins fall somewhere between identical and fraternal twins.

With half identical twins an egg is fertilized by two sperms and later divided into two embryos.

Half-identical twins share at least half of their genes.

It is also believed that semi-identical twins share identical genes from their mothers’ side (as one egg is only fertilized) and only share half of their genes from their fathers’ side.

The chances of conceiving in this manner is very rare though.

1 Comment

  1. lori smith

    my grand daughter were born 2 sacs 1 placenta but their sacs was together in a large sac they were born same weight same measurements same blood type the doctor said he’s never delivered twins that were exactly the same . but here’s the funny part now they are 6 yrs old and are completely opposite one tall brown hair brown eyes one short blonde hair blue eyes and are opposite in every way one like ketchup the other mustard one Pepsi one coke one peanut butter one jelly but are very close they tk care of one another one won’t leave the other it’s beautiful

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