Board Thread:Boruto: Naruto the Movie/@comment-5054236-20151013101237/@comment-734582-20151117230510

MarshalLee.TheVampireKING wrote: I think that the only logical answer is that Gaara is his father. The fact that he battle and wins to metal Lee basically proves it. Boruto the movie got quite a few easter eggs or callbacks to Part I. Like, it has the Lions barrage combo with both Sasuke and Naruto (who both stole the movie from Rock Lee), Boruto's combo with Sasuke is a clear callback to the move against Zabuza, and a few more things i forgot.

So yea, the fact that Metal Lee loses against him pretty much proves it's Lee's kid.