My brother and his girlfriend seem like they’re going to be together for the long haul, and I know that he at least wants kids. There are lots of twins in our family (our maternal grandmother was the older sister of twins who died as toddlers, and two of her brothers had twins themselves. Our dad has at least one set of twin cousins too) and my brother’s girlfriend is the older sister of twins as well. I’m not positive about one set of cousins, but I know all the rest were fraternal twins.
Would teasing them about having higher odds of giving me twin nieces or nephews be reality-based?
For what it’s worth, when my ex- and I learned we were having twins, we were told that ancestors having fraternal twins is really only meaningful in the mother’s family. I didn’t ask at the time, but I assume that that’s based on the assumption that it’s a trait that makes multiple ova ready for conception at the same[-ish] time.
Relevant background, if not exactly an answer: when we lived in Mozambique we were told that country had the highest rate of twin births in the world. I have just tried to get a cite for this and the closest I could come was some pan-African study suggested in 2002 because:
I started to try to back that one out statistically to see if the numbers support the implied claim, which is that Africans are more prone to having twins than the rest of the world. I gave up, though - I gotta get back to work.
Assuming the numbers do show that a disproportionate number of twins are born in Africa, this doesn’t tell us why - is it genetic? Something in the water or soil?
In vague, anecdotal, completely unscientific support of the latter, friends of ours who were expatriate Caucasians conceived twins while living in Mozambique, despite no family history of duplets. OTOH, I too got pregnant there (in room 512 of the Polana Hotel, if you must know ) and thankfully only have one rambunctious kid to show for it.
IIRC from when ChinaWife was expecting, twins in the family increase the odds. having kids post-35 years old for Mom REALLY increases the odds of twins (regardless of twin birth history in the family).
BTW, china wife was 36 when we had twins, and no twin history on either side of the family.
I think the highest twinning rates are among the Yoruba (roughly Nigeria)–the religion (Ife?) traditionally holds twins in very high regard, but I don’t know which fact selects for the other. IIRC (I’m a twin so I’ve looked into this before) fraternal twinning has a genetic factor for likelihood, while identical twinning does not.
If it’s true that it only increases the odds of twins if there are twins in the mom’s family, wouldn’t that make it mightly coincidental that two of my great-uncles had twins, then? “Only” 8 kids in that family made it to adulthood (as I said, their twin siblings died very young) and 1/4th of them when on to have twins themselves.
One of the suggested reasons for high rates of fraternal twins among the Yoruba is the consumption of large quantities of yams.
"Yam consumption may be one explanation for Africa’s largesse, some West Africans and Western experts believe. Yams contain a natural hormone phytoestrogen which may stimulate the ovaries to produce an egg from each side. "
No, because genetic factors are only one of the causes of twins. Fertility drugs account for a large increase in multiple births, but age is also a significant factor: the older the mother is when she conceives, the more likely she is to conceive fraternal multiples.
If fraternal twins are hereditary, what about monozygotic? My mother has identical twin brothers. She had two sets of identical twins, and my sister who is a twin married a man who was a twin and she had identical twins.
This has always interested me, as my mother is a fraternal twin and my husband’s father is a fraternal twin. My husband’s first cousin just had fraternal twins as well, so it definitely makes one think there’s a connection.
My grandmother (now 93 and with only a couple of days to live, sniff…) is probably an identical twin - it was never tested but she and her sister are so identical that my father as a little boy when they all lived together during the war, would work out if it was his mother by smelling her! Sight was not enough, particularly as they shared rationed clothes at the time!
Granny’s mother had eight children, all twins. Granny and Aunty were the first set and then there were two sets of girl/boy twins who were obviously fraternal. G. Granny was a couple of weeks off giving birth to the fourth set when she died and the twins were buried with her, unborn, so no-one knows what they were.
My brother and I are fraternal twins but it’s my father’s mother so maybe no connection.
There are no other twins in my cousins or their children so the madly twin producing factor seems to have stopped at my great grandmother.