Board Thread:Boruto: Naruto the Movie/@comment-5054236-20151013101237/@comment-27234598-20151117223611

I think that the only logical answer is that Gaara is his father. He possesses the Magnet Release Kekkei Genkai, so if he is the son of a known character, he had to have inherited it from one of them. This narrows it down to only 8 characters. Of those eight, only three of them are from the hidden sand: Rasa (Gaara's father), Shukaku (One tail), and Gaara. Of these, Gaara is obviously the only logical answer. And on top of all of that, he controls SAND!!! And sand is definitely a Gaara thing.

I really have next to no doubt about it.