You honestly don't know who Justin Bieber or Jesse McCartney are? You must not be from America, Canada, or the UK then.
Justin Bieber and Jesse McCartney are both "pretty boys" that make bad mainstream pop music, Justin Bieber being about 17 and Jesse McCartney being about 24. Justin Bieber is a douchebag who has avoided trouble with the law thanks to his guards and his fame, and his rep for looking, acting, and sounding like a girl is so prominent that he has even poked fun at it in a commercial featuring him. His 7-year-old-boy haircut used to be a meme because it was so creepy and feminine, until he had it trimmed without telling his contractors that made merchandise like DOLLS of him. People seem to think he's homosexual. He STILL made tens of millions of dollars on his song "Baby". Jesse McCartney makes R&B/Pop type music and is an actor on some show about a beach and teenagers. He currently struts around in his music videos with his hair black and done up like Leonardo DiCaprio. He used to make cutesy love songs like "Beautiful Soul" and "Because You Live," but now his songs are more rap-like.
Jesse McCartney is a pop music artist, he started out as a pre/young teen in Dream Street. Then at 17 he went solo and put out the hit "Beautiful Soul". A couple years later he dyed his hair black to look like a young Leonardo DiCaprio and started making making more R&B/rap type pop music...that sucked, in my opinion. He's also an actor.