Sean Kingston Wanted His Bro’s ‘Beautiful’ Girl, On ‘When I Was 17′

'Beautiful Girls' singer says he didn't know the pretty lady was his big brother's GF on Saturday's episode.

Somebody call 911! [artist id=”2542027″]Sean Kingston[/artist] pulled a robbery on his big brother, he reveals on this week’s “When I Was 17.” According to the “Beautiful Girls” singer, though, he had no idea he was making moves on his brother’s girl!

“I remember one time I tried to hit on my brother’s girlfriend,” Kingston says on the episode airing Saturday at 11a.m. ET/PT on MTV. “[I] didn’t even know it was his girlfriend.

She must have been hotter than the sun in the south of Spain because Kingston was smitten as soon as he laid eyes on her. “She came over to the apartment and it was like 2 o’clock in the daytime,” the pop star recalls. “As soon as I opened the door I was like, ’Man, she’s so beautiful.’ ”

Kingston’s brother, unaware of his little bro’s charm, suspected nothing at first. “I left the two [of them] in the living room and then I went to go get some food,” he says.

Kingston, of course, took advantage of the opportunity.

“And that’s when I made my move,” Sean explains. “I just tried to hit on her. I was like, ’How you doin’ sweetheart?’ You know, we were talking about different things. I was telling her what I was doing with the music thing and she was telling me she was trying to get into the modeling thing. So we had a great conversation.”

Until they were interrupted: “I remember my brother coming around like, ’Hey, what you doing, man? That’s my girlfriend, man.’ ”

“When I Was 17″ — this week featuring Sean Kingston and Mark Hoppus and Tiffani Thiessen — airs on Saturday at 11 a.m. ET/PT on MTV.