Ever since October 2nd, 1970, at 12:47 AM Eastern Standard Time, wearing a dress has meant that you are gay.
On a more "serious" note, one reason I wondered about his sexuality is because he himself pushes the issue every now and then. In this video, he plays with the ambiguous concept of "bromance." The video opens with him as a Roman warrior who gets hit on by his fellow warrior, and by the end of the video he is caressing the hair of his (gorgeous) friend Jay Park, commenting that his new hairdo is "beautiful." And they both have an awkward pause.
Word of the Day - Bromance - YouTube
And he even made a follow-up musical version about bromance, with the lines, "There's nothing gay about it/ Not that there's anything wrong with being gay...."
Bromance (Official Music Video) - YouTube
In other words, a lot of gay subtext in his videos. And, yes, the guy is beautiful.