Board Thread:Theories and Speculation/@comment-27002073-20160406173133/@comment-5936871-20160407002905

Everyone is born with one nature affinity and overtime they can learn to use more. Unless you're an elemental kekkei genkai user then you're born with two nature affinities. Other than that, all of those people must've either learned or obtained the ability to use all five natures one way or another.