is/are more common in some families (indicating genetic influences), in some racial ethnic groups, and in women who use fertility drugs.

Dizygotic twin

Explanation:

Dizygotic twin is also known as fraternal twin, it occurs when two separate ova, or eggs, that are released at the same time from an ovary and are fertilized by separate sperm. Many women make use of fertility drugs, that facilitate or stimulate the production of ova, increasing the chance of multiple births. Dizygotic twins are more common in some families and also in some racial groups, because more women are having babies in their 30s, and that is the time when fertility start dropping in women.

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explanation:

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