It is estimated that out of every 1,000 births in the United States, 33 of them are twins. Identical twins occur when a single egg splits at the last moment, and each of those begin to develop as a separate embryo. However, on rare occasions, twins are actually born from two entirely separate eggs. Twins born under these conditions are known as being fraternal and are not identical in appearance or genetics.
The twins featured in this video are at the age when they are beginning to talk. They aren't able to use any actual words, but conversing in baby talk is an important step in their developmental progression. Seeing them mimicking speech patterns is as important as it is adorable.