It's a Big Brother, Best Friend Forever Ballad! Coconeru covered B.B.B.F.F. in a slowed-down, piano-ballad style. It sounds really sweet and fits the emotion of the song perfectly. I also like the backup singers. :)
Give the song a listen in the video. As always, you can find Coconeru on Youtube, where he's uploaded plenty of other pony covers and originals.
Coconeru, thanks for sharing your singing and ballad-writing talents with the site! Keep up the good work.