If my husbands grandmother had identical twin daughters and his mother had only sons what are the chances of the boys having identical twins too?

Answer 1

Neither the husband, nor his family history of twins, will have any effect on his sons fathering twins. Whether or not a pregnancy is twins, triplets, etc., depends entirely on the woman. What determines twins (or triplets) is if one egg is fertilized, then splits in two, then this is identical twins; if the egg splits in three, then it's identical triplets. If two eggs are fertilized, then they will be fraternal twins, and not identical, and may not even resemble each other at all; they can even be a different sex from each other. If three eggs are fertilized, then they will be fraternal triplets, and not identical, and can be all female, all male or two of one sex and one of another. The bottom line is, the father neverhas anything to do with whether or not it's a single birth, twins, triplets, etc. It is the mother, and the mother only. Now if multiple birth pregnancies run in her family, then the chances of twins will be higher than families with no history of multiple births.