Board Thread:Theories and Speculation/@comment-24824859-20160108012905/@comment-734582-20160108083738

Since Byakugan is from Hamura's line and is on both the Moon and on the Shinobi World, it's likely Hamura had a bunch of kids that contributed to the Kekkei genkai pool.

However, i think it's fairly clear that chakra responds differently to different people, kekkei genkai can also be the result of people's own genetics in combination with the ability to create chakra. After all, Hagoromo only gave the ability to use mental energy, and the Shinobi merged it with their own physical energy to create chakra.