Board Thread:General Discussion/@comment-1918136-20131119033214/@comment-1504072-20131119134614

Despite the genetic modifications, Solid Snake was still cloned from Big Boss's genes, even if he is not 100% identical. Solidus is always referred to as a "perfect clone," but even he is not a 100% match due to mitochondrial DNA inheritance from the egg cell donor used in his creation (although the DNA in his cells' nuclei is identical).

And if you want to get technical, the clones are actually more like siblings genetically, rather than offspring, since they and Big Boss all share the same genes from Big Boss's parents. Big Boss acknowledges this by calling Solid Snake "brother" in their final meeting.

Anyway, food for thought.