I've found 3 sets of twins in my family.
The most recent were my sisters kids. When she was pregnant with her first child, she was asked by the doctor if there were twins in the family and she asked me. I told her NO there are not.

Fortunately her first child was a singleton. The second pregnancy she had twin daughters. They are now aged 15.
After my neices were born I did some more digging and discovered that our grandmother had twin boys (my fathers older brothers) but one of the twins had died very young.
Since doing my family genealogy, I have discovered a third set of twins in my gt gt grandfather and his brother.
BD