Board Thread:Questions and Answers/@comment-32018183-20170515182755/@comment-29325824-20170515193005

Well since Bicorns aren't said to be directly born, but instead are mutated Unicorns, I can imagine two things happening: Either they give birth to Unicorns (though will probably try to convince their child to become a Bicorn asap), or their child turns from a Unicorn into a Bicorn in utero due to her energy being corrupted that early.

See, it is said that mutational variants tend to give birth to their parent species, though have a higher chance to give birth to their own variant.

Either way, I don't see a lot of Unicorns coming from Bicorn families.