Long-lost twins

A few weekends ago, while watching television at my boyfriend's house, a movie comes on, and his mother leaves it on. The movie is Two of A Kind with Mary Kate and Ashley Olsen. I loved this movie as a little girl, and watching it again, i realized again my love for this movie. However, I got to thinking about it and all the other movies that feature twins and came to the conclusion that just about every set of twins featured in a television show or film are long lost twins.
Two of a Kind is this kind of movie. Well actually it is a bit different.In the movie, Mary Kate and Ashley's characters are not twins, but two very different girls that look absolutely identical. They find each other at camp, and begin trying to set their respective guardians up so they will fall happily in love. The trick works and Steve Guttenberg and Kristie Alley's characters fall for each other and the end of the movie reveals that the whole thing was a set up by the two identical looking, but not twin, girls.
Another more famous version of this is The Parent Trap. This is the movie that made the long lost twin story famous. Two girls go to camp, find each other, and realize that they are identical twins. One twin lives with the mom, the other twin lives the the dad. They realize all of this and at the end of camp they switch places to visit the other parent. At the end, they reveal their true self and have to make the switch back, all while trying to convince their parents that they truly are still in love and can make it work.
A television show that also had the long lost twins was "Sister Sister." This show was about two twin girls that found the other while shopping in the mall. One had been adopted by a woman, the other by and man, and when finding out they each had one half of a set of twins, they moved in together and tried to make it all work out.
It seems that whenever there are twins, they have been separated at birth and find the other at some point in their life. Once making this discovery, they also try to get their parents to fall madly in love and move in together or get married.