Board Thread:Naruto: The Last Discussion/@comment-732150-20150205151208/@comment-24593592-20150213013847

Hisana456 wrote: @Elve, that won't be alien abduction; it would be true love. Yeah, it would be cool to know that Hamura had a heart to make this woman the first human to walk on the moon! Therefore, human genes might run in both Hyuga and the current Otsutsuki. Toneri and his fellow clansmen seemingly don't have horns.

I think Kaguya and her kids having horns is due to Senjutsu absorption. Like Juugo and curse seal users.