Les Enfants Terribles

The Les Enfants Terribles project, a project in which the main aim was to create the Sons of Big Boss. It was discovered that Big Boss was sterilised during a nuclear explosion. This was most likely caused by his exposure during nuclear testing at Bikini Atoll or because of the explosions caused by the Davy Crocketts.

Sons of Big Boss
A few years later when he was in a coma after a fairly radical mission, the government decided to take some of Big Boss' DNA in order to make clones of him. In the project, one of the clones was to carry all of Big Boss' recessive genes(Solid Snake), one was to carry all of his dominant genes (Liquid Snake), and one was to have a perfect balance of dominant and recessive genes from Big Boss (Solidus Snake).

During the Shadow Moses Island incident, Liquid Snake was under the impression that he was the inferior, having been granted the supposedly "flawed" recessive genes, whilst his brother recieved the "superior" dominant genes. Hence his resentment towards Solid Snake during their confrontation and his believing himself to be "Garbage from the day (he) was born", the leftovers of what they had used to create his brother, "the Legend", Solid Snake. In truth however, it was Solid Snake who was the genetic "inferior" spawned by the project, whether by accident or design.

Yet in spite of his supposed genetic shortcomings, it was Solid Snake who battled and defeated both Big Boss and Liquid, proving once and for all that genes do not dictate one's fate.

The Super Baby Method
It is revealed at the end of Metal Gear Solid that from one of Big Boss' cells, eight embryos were created. Liquid tells Solid that the other six were destroyed so that they could create Solid and Liquid. However, the number of aborted fetuses might be incorrect, as it is later revealed that there is a third surviving clone that Liquid did not take into account.