Identical or Fraternal???

Since we found out that we are having twins, people have asked many questions. Are they identical or fraternal? Do you have twins in your family? Are they boys, girls, or one of each? 

On next Monday, we will find out if they are identical or fraternal and possibly the sexes, even though it is still early to see that at 16 weeks. The doctor has ordered an MRI to determine what type of twins they are. He said that if they are identical, he will have to monitor them more closely. When he said that, it sparked my interest and this is a little of what I learned about twins.

Identical

Identical twins are created from one fertilized egg that has split and they share the same genetic information. Identical twins may share the same placenta and amniotic sac. Twins being identical is an anomaly and is not hereditary.

Fraternal

Fraternal twins are created when two eggs are fertilized by two different sperm cells and they are genetically unique children (two siblings born at the same time). Fraternal twins can be the same sex or different sexes or look similar or look different. They can be as similar or different as any other siblings, but are born at the same time. Fraternal twins have separate placentas and amniotic sacs. Fraternal twins can be the result of several factors, including heredity.

Twins are hereditary in both of our families, but according to research this trait can only be passed through the mother. Some families have the hereditary trait of releasing two eggs at the same time during ovulation.

In earlier ultrasounds, they appeared to be identical, but K has this hereditary trait. So, what do you think they will be: identical or fraternal?