On the radio this morning I heard that a woman in Bosnia had given birth to twins, each of whom had a diffirent father. I’m not going to ask if this was true or not, but if it’s possible. It sounds faintly plausible, but so do most of the great myths and urban legends. So, could a set of twins have the same mother and diffirent fathers?
Identical twins: Not possible.
Fraternal twins: Sure. One egg gets fertilized by one guy’s sperm and a second egg gets fertilized by a second guy’s.
Quite unusual, to be sure, but theoretically possible.
Yes, if they are fraternal twins.
I don’t know how likely it would be, but since fraternals come from two separate eggs, I guess it would be feasible that two separate men could fertilize one each.
At least, that’s my take on it, until someone who’s an expert on this comes in to prove me wrong. But my basic memory of biology serves me with the above…
always check the archivesfirst.
Yes, but it’s extremely rare for a few compounded reasons:
Twins are fairly rare
Most women don’t have multiple sexual partners (not within a few hours of each other anyway)
It will only work if it’s fraternal twins where the egg has split (or two eggs are released) before fertilisation; if the split occurs after fertilisation, you get identical twins, which can only be the product of the same parents.
I have also heard (and this is just anecdotal) that fraternal twins can be conceived at different times.
If, for instance, a woman produces two eggs and they are released two days apart, or travel at different rates, egg 1 could be fertilized on, say, Monday, and egg 2 could be fertilized on Wednesday. Difficult to prove, I imagine, but I don’t think impossible.
Does this question give me the chance to use one of my favorite words:
Superfecundity
Doesn’t it?
I think there’s a small stistical chance the two could still be identicle - granted it would be about a 1 in a few billion or greater shot.
Bob55 – the deal with identical twins is that they are the process of one fertilized egg dividing into two - thus both zygotes and therefore both children contain the exact same genetic material, meaning they must have the same father because they have the exact same DNA. So it would be impossible for identical twins to have different fathers.
As for fraternal twins, which come from two separate fertilized eggs, it would be possible, theoretically, though the chance would be low. I know it happens with cats, different kittens in a litter having different fathers, but I’m assuming there are some different systems going on there anyways, so maybe that’s not a good example. 
There was a case IIRC where a woman gave birth to a black baby and a white baby at the same time.
What if she was porking two identical brothers?
This one has already been answered, and the answer is yes. Still, I wanted to point out that sperm doesn’t die off after an hour or two; rather, the uterus can nourish sperm and keep it alive until it’s needed - about 5 days or so. And since we’re talking about fraternal twins, the two eggs don’t need to be released at the same time, and probably won’t be - they could be released several days apart. So, and I’m not sure of the exact time frame (I’m just too lazy to look it up, I can do so if anybody objects), our theoretical slut has probably about a month to do her sleeping around.
I’d guess that many women who have fraternal twins from different fathers don’t know it. All the historical cases deal with a pair of babies of whom one is white and one black, coming from white and black fathers. Now, technically, one can get babies of very different skin colors from the same two parents; but I’d also be willing to bet that if the two fathers are of the same race, the mother probably wouldn’t think of the possibility.
And, Bob55, “a few billion” isn’t even close. Fraternal twins fathered by the same guy (forget unrelated people) have a 1/70,000,000,000,000 (that’s one in seventy TRILLION*) chance of having the same chromosomes, and this doesn’t begin to take into account crossing-over, which is a variable amount of “fudging” that goes on between chromosomes before they are separated. So, um, no. The chances of fraternal twins by two different fathers being functionally identical is probably less than your chances of quantum-migrating to Zimbabwe in the next 30 minutes.
(*) that’s (2^32)^2
You should post more often!
Thanks, UncleBill. I just wanted to add that I got my numbers wrong in the original - I underestimated. By a lot.
The probability of packing up a given set of 23 chromosomes into an egg or sperm is 2^23 (a choice of two - maternal or paternal version - and 23 such choices). I squared that because you’d have to multiply the chance of Father #1 getting that order, by the chance of Father #2 getting that order. If we were talking about two sperm fertilizing one egg, that would be correct - but that’s NOT what we’re talking about. We’re talking about two sperm fertilizing two eggs. Both pairs have to be identical - so we raise it to the fourth, not eh second, power.
The chance of fraternal twins having the same assortment of chromosomes, not counting the ever-present crossing-over, is 2^23^4, or 5,000,000,000,000,000,000,000,000,000 or FIVE OCTILLION (that’s 10^27, or in the ballpark of Avogadro’s number times 10,000) … and remember, this is still assuming the same father (or I suppose identical twin fathers).
We can discuss this in Zimbabwe in 30 minutes.
Not even then since the sperm would be different. The chances of two sperm from the same individual (or from a man his identical twin) being the same are too low to be worth calculating.
What I meant was that there’s ~3 billion base pairs in the human genome. Statistically 2 people, regardless of the father, could have the exact same DNA through recombination. The chances would be incredibly low though, how many ways can you rearrange 3 billion base pairs? (like one in 3 Billion factoral?). Of course this doesn’t take into account epigenetic effects on the zygote’s DNA.
I’ve heard of a similar case, if not the case you’re thinking of, but it was the result of an IFV tech error, not a woman sleeping with two different men. The last I heard they were in court with the bio dad of the baby that wasn’t her husband’s, since she wanted to keep both babies.
Er, make that IVF. I knew something looked strange…
Even if you hit these odds and created twins with different fathers with identical genome sequences, they’d be fraternal twins. By definition identical twins come from a fertilized egg that splits into two people, and fraternal twins come from two differeent sperm/egg combos. So it is Impossible to have identical twins with two different fathers. It is possible to have two fraternal twins with identical DNA sequences, though extremely unlikely.
I remember reading about that in Jet, although there they said the families amicably reconciled, with children going to the correct parents. However, that’s different from the case cited in Cecil’s article here, which happened in 1810.