In case nobody said it already: (Heavy MGS1 spoilers) Solid and Liquid are clones created by an advanced genetic experiment. They hand-selected the genes that went to each person. That's what made them special; they were amped up clones of Big Boss.
Also...Liquid got the recessive traits but was the "better" clone, in terms of the traits the cloners wanted to emphasize. His handlers always told him that he was the reject, the inferior clone, the refuse from the superior Solid Snake.
This was a lie. They wanted Liquid to feel inferior so that he would fight harder to make up for his perceived deficiencies.
---
I write Naruto Fanfiction. But I am definitely not a furry.