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How are fraternal twins related to the release of more than one egg?

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Detailed cross-sectional illustration of a human ovary showing the stages of follicle development, ovulation, and corpus luteum formation, with labeled structures including primordial, primary, secondary, and mature follicles, a ruptured follicle releasing an ovum, and corpus luteum and albicans. An inset at the bottom shows the ovary's location in the female reproductive system. — ovary The steps of ovulation, beginning with a dormant primordial follicle that grows and matures and is eventually released from the ovary into the fallopian tube.

Fraternal twins, also known as dizygotic twins, are directly related to the release of more than one egg during a single menstrual cycle.12

Normally, the human reproductive system releases only one mature egg at a time. However, when multiple ovulations occur, two or more eggs may be released from the ovary simultaneously. If each of these eggs is fertilized by a separate sperm, they develop into individual zygotes.3214

Because these siblings originate from separate eggs and separate sperm, they are not genetically identical; they share, on average, half of their genes, similar to any other pair of siblings. The occurrence of this multiple ovulation can be influenced by various factors, including family history, maternal age, and the use of fertility drugs, which are specifically designed to stimulate the simultaneous release of multiple eggs.12