Very interesting.
Women who are in their 30s are more likely to have twins
Women who take fertility drugs are more likely to have twins
Twin rates are about 3%
Many twins are premature and have to spend time in neonatal care.
I had a first cousin once removed who was a twin--her twin sister died at birth but she lived to 96. Their mother was 30 when they were born.
My grandmother and her brother were twins--their mother was 26 when they were born. I have a second cousin who had twins when she was 26. One of them is the father of twins who were born when their mother was 30. My other grandmother had younger sisters who were twins, born when their mother was 34.