Statistics show three out of every 100 births deliver twins.
Vickie and Curtis Eberle aren't statisticians, but they're crunching the numbers after Vickie delivered twins Monday, two years to the day since she gave birth to their first set of twins.
"It's very much more demanding," said Vickie Eberle. "You're thinking, 'OK, whose diaper did I change? Who ate last? Did I do it twice?'"
The Prairie du Sac couple's first set of twins was born two years ago.
"We're set for probably five or six more years of two car seats," Curtis Eberle said.
"I just know that once you have twins, it's a greater chance of having them," said Vickie Eberle.
The chances are greater when a person has given birth to twins before, and families have multiple sets of twins more often than some may think.
But what makes the Eberles' situation rare is that the couple's two sets of twins share the same birthday -- Jan. 28.
"Even having the same birthdays for just singletons is rare," said Vickie Eberle. "It's just got to be astronomically rare for having twins on the same day."
People can calculate the odds and find probabilities, but the Eberles said they're content just to count their blessings.
"I just feel like I'm blessed to be able to have these children and raise them, and that that the good Lord is giving us what we need," said Vickie Eberle.