One of the parental twins may be a girl and the other may be a boy . Why ?
Answers
the identical twins are always of the same sex because they form a single zygote that contains either male (xy) or female (xx) sex chromosomes
a set of boy /girl twins can be fraternal boy girl twins cannot be identical
they can be girl and boy which means the mother conains two zygote of a male and female which has xy and xx chromosomes
If the egg when fertilised after fertilization can split into two different fertilised eggs they are known as identical twin. Here in the case of identical twin both the fertilised eggs are of same gender. And for fraternal twins one can be male and other can be female or any one of the one. So one of the parental twins may be a girl and another can be a boy explained in the case of fraternal twins.