I definately think that is baby Captain Hook.
His casting call describes him as “a free-spirited 10-year-old who is mourning his mother’s tragic death.” Owen has also been described as “a precocious, strong-willed kid who isn’t afraid to speak his mind — but his free-spirited, lively personality is all a facade, as he’s secretly dealing with the tragic death of his mother.”
http://onceuponatime.wikia.com/wiki/Owen
This is exactly how Hook behaves- its all a mask to hide his pain.
I would be very surprised if this wasn’t little baby Killian Jones. The directors did also say that we will soon see more of Killians’ background and Neverland in a recent interview.
Also, I think he could also be Killian because the directors are setting up Emma and Killian. So it would make sense that Killian would also be an orphan with a difficult past, because Emma and Killian would be able to relate to one another (if possible) even more and help to heal each other.