Fraternal twins.
Back in the old days there would be two single beds in a husband and wives bed room. Hence, twin beds.
Chang and Eng Bunker ( as I recall, no relation to Archie) were the first pair to survive to adulthood and they hailed from Siam. (they were male) hence the name. It is a congenital anomality and is...
Yes.
four babies born at once is called quadruplets.
Vanishing Twin Syndrome