Fraternal or Identical?

JennP03

We ran into a gentleman at the park who has 31 year old twin boys.  When I asked him if they were IDs or fraternals his response was, "Well there's more to it than that. They're a little of both." I assumed her was referring to them being mo/mo, mo/di or di/dim, but then he went on to tell me about how they are part identical.

I have b/g twins, so obviously fraternal unless you're one of those smart people who think b/g twins can be identical, but I thought it was pretty clear cut.  IDs are from the same egg and fraternals are from two separate eggs, right? He just doesn't know if his are IDs or frats, there's not something I'm missing is there? Sorry if this seems like a dumb question. I didn't want to get into a long discussion with some guy I don't know about the zygosity of his twins, but afterward it got me thinking about what he meant.

pea-kay

Oh dear. I think he just didn't know what he was talking about, frankly.

LegallyBlonde217

I think I've heard of that before.  I believe that's allegedly what Mary Kate and Ashley Olsen are. It's where 2 sperm fertilize the same egg, then the egg splits.  I could be wrong, though. 

ETA: This article states the Olsen twins are fraternal, but he does explain "half twins."

caden

There is such a thing as semi-identical twins but I think they are very, very rare. Like, in 2007 there was only one confirmed set.

JordynLeighx3

Google "Polar body twins" it's where the egg splits and is then fertilized by two separate sperm.
It's more of a theory that can be assumed but not really tested to my knowledge. They share 75 percent DNA whereas ID are 100 and frats share 50.