A twin is one of two offspring produced in the same pregnancy. Twins can either be monozygotic ("identical"), meaning that they develop from one zygote that splits and forms two embryos, or dizygotic ("fraternal") because they develop from two separate eggs that are fertilized by two separate sperm.

In contrast, a fetus which develops alone in the womb is called a singleton, and the general term for one offspring of a multiple birth is multiple.

The twin birth rate in the United States rose 76 percent from 1980 through 2009, from 18.9 to 33.3 per 1,000 births. The Yoruba have the highest rate of twinning in the world, at 45-50 twin sets (or 90-100 twins) per 1,000 live births, possibly because of high consumption of a specific type of yam containing a natural phytoestrogen which may stimulate the ovaries to release an egg from each side.

The world's highest rates of twinning are found across Central Africa, where there are 18-30 twin sets (or 37-62 twins) per 1,000 live births. In Latin-America and South Asia and South-East Asia the lowest rates are found; only 6-9 twin sets per 1,000 live births. North America and Europe have intermediate rates of 9–16 twin sets per 1,000 live births.

Larry and Laurent Bourgeois, popularly known as "Les Twins" or Larry " Ca Blaze " Bourgeois and Laurent " Lil Beast " Bourgeois, are a hip hop dance duo originating from Sarcelles, France. The twin brothers who are of Guadeloupean descent (Guadeloupe, F.W.I.), are known worldwide for their talents in New Style dancing. Although they can be seen dancing as a duet, they are also a part of a larger crew known as Criminalz Crew, a group with a variety of dancers that range from b-boys to other new style dancers such as themselves. Les Twins have appeared on the television show Incroyable Talent as well as the Ellen DeGeneres Show. Les Twins have competed in multiple dance competitions such as: World Of Dance, Battle Of The Stylez, Urban Dance Showcase and won the Juste Debout Dance Competition in the Hip-Hop New Style category in 2011. ^{[original research?]} They come from a very large family with 18 siblings, and only 9 of whom dance.

Les Twins have performed with Beyoncé Knowles. They have also appeared in Jay-Z's That's Rocawear viral video and the music video for "La Gloria" by French-Argentine band Gotan Project. They were also traveling with Cirque du Soleil Michael Jackson Immortal World Tour as dancers with a newly formed crew especially for the tour, named Veteranz crew until sometime in 2012.

James Douglas Muir "Jay" Leno /ˈlɛnoʊ/ (born April 28, 1950) is an American stand-up comedian and television host.

From 1992 to 2009, Leno was the host of NBC's The Tonight Show with Jay Leno. Beginning in September 2009, Leno started a primetime talk show, titled The Jay Leno Show, which aired weeknights at 10:00 p.m. (Eastern Time, UTC-5), also on NBC. After The Jay Leno Show was canceled in January 2010 amid a host controversy, Leno returned to host The Tonight Show with Jay Leno on March 1, 2010.

James "Jay" Leno was born in New Rochelle, New York, in 1950. His mother, Catherine (née Muir; 1911–1993), a homemaker, was born in Greenock, Scotland, and came to the United States at age 11. Leno's father, Angelo (1910–1994), who worked as an insurance salesman, was born in New York to immigrants from Flumeri, Italy. Leno grew up in Andover, Massachusetts, and although his high school guidance counselor recommended that he drop out of school, he later obtained a Bachelor's degree in speech therapy from Emerson College, where he started a comedy club in 1973. Leno's siblings include his late older brother, Patrick, who was a Vietnam veteran and a lawyer.