So my husband and I assumed identical twin boys given we had a single embryo transfer At the week scan, they asked us if we wanted to know the sex of our babies and we said we already knew one was a boy and assumed the other was as well Anyway, imagine our surprise when they said one was a girl and one was a boy!!!!! Two boys and identical twin girls He is the author of the popular books Dad's Guide to Twins and Dad's Guide to Raising Twins This site is dedicated to helping you learn from his experiences (and thousands of other twin parents) so you can be the best twin dad you can beIn 999% of cases boy/girl twins are nonidentical However, in some extremely rare cases resulting from a genetic mutation, identical twins from an egg and sperm which began as male (XY) can develop into a male / female pair This happens when the fertilised egg 'loses' one of the copies of the Y chromosome when it is dividing into two

Identical Twin Teenage Boys Tell Story Of One Taking Path To Become A Girl New York Daily News