You do have an increased risk of delivering prematurely.
Yes, there is 4 sets of identical twins in every 1000 births.
Although there is a genetic component to twin births, many multiple births are not genetic. If one generation has twins, the next generation may also have twins. The likelihood of twins reduces with succeeding generations that do not have twins. Multiple births does not have patters such as generation skipping, and is never guaranteed.
1/1000 births = 0.001% of calves are born as twins.
The rate of twinning varies by country. There were 33.9 twins born for every 1,000 births in 2014 in the US. Yes, the rate of twin births has been increasing.
In the US, the incidence of fraternal (dyzygotic) twins is 32 in 1000 live births.
Not very often. It is more common for a cow to have twins than triplets: triplets occur maybe 1:100,000 births. A cow will have twins 1:1000 births.
Conjoined twins happen about once in every 50 thousand to 200 thousand live births. Live births on average happen every 39 seconds in the USA.
The Duggar children closest in age are the twins, as they were only born minutes apart. Other than the twins, the closest births are Jordyn and Josie, at 8 days less than a year. Jordyn was born on December 18, 2008, and Josie was born on December 10, 2008. However, Josie was born four months premature, so if she was born on or around her due date, they would not be the closest in age.
The ratio is around 1 in 1000 births.
It has the highest rate of twins births in the world.
Siblings can be the same age, in the form of twins and triplets, and other various forms of the multiple births.
The frequency of having monozygotic twins (identcal) is about 4 out of every 1000 births. Whereas dizygotic twins (fraternal) is about 12 out of every 1000.