Well, time for a nerd moment!
YAY!
So, only one video with a sighting of Herobrine was actually canon (real) the rest have just been fake-outs either with mods or with friends/family with the herobrine skin and the name Herobrine. So, no he isn't real anymore. He got patched up after the first sighting, (Even I don't beleive the first sighting was real). So not really!
More? use this link.
But, lots of people beleive he's real so, if you're trying to blend in say he's real if factually acurate (what I go for) say no.
So, in vanilla no. In chocolate (what I call modded) yes
Thanks.