But there is a flash of temper when Roger Clinton sees a photographer. He hasn't showered, he complains, bouncing around the room where he has come to be interviewed, and he doesn't think his look is right.

When someone offers to lend him a shirt, he blows up, talking fast and plucking at his T-shirt: ''You see, you see - I didn't mention the shirt. You mentioned the shirt. You think there's something wrong with my shirt, or you wouldn't offer me a different one.'' Once the photo shoot is rescheduled, in front of a Burbank mural featuring James Dean, sunshine returns.

''James Dean is good, because speeding is one of my weaknesses, too,'' says a laughing Clinton, who cruises L.A. in a silver, twin-turbo, all-wheel-drive Dodge Stealth sports car.

The cellular phone rings.

''Hello, hello, this is Roger,'' he says, sitting on a terrace overlooking the city, his right leg jittering to an invisible beat. ''Hi, Dave, how are you? That's OK, buddy. Oh, are you kidding me? Man, that's great. I got to do that. That'll be great. I'd love to be on the cover. OK, thanks buddy.'' He puts down the phone. ''Hey,'' he says, his face bursting with a huge grin. ''National Lampoon wants to put me on the cover of the next issue. I'm such a big fan of National Lampoon magazine since I'm a kid.'' Overcome, he puts his head down on the table for a moment and then lets out with his big, braying laugh: ''I love it!'' With presidential half siblings falling from the sky, Roger Clinton is not wasting any time ''going after it,'' as he likes to say.

The 37-year-old half brother of Bill Clinton - the future president was adopted by his stepfather Roger Clinton and took the Clinton name - is feasting at the buffet of nepotism, grabbing goodies with both hands, pitching and catching offers for commercials, endorsements, albums, musical gigs here and abroad, autobiographical and inspirational books, lectures, movies and personal appearances, as at this year's opening of trout season in upstate New York.

Some big deals have fallen through - a possible endorsement for Coke or Pepsi and an album with several guest stars that was to have been produced by Atlantic Records.

And there have been some embarrassing moments - the incident last spring when he earned the tabloid sobriquet ''Ragin' Roger'' after he had a tussle with a spectator at a Knicks game in Madison Square Garden, for example.

He has a manager and two agents and he is shopping for a literary agent. He is the Peter Pan of First-Brother Land, as he calls it, and he bubbles with ideas, one for a generic cola commercial featuring his letters on his brother's campaign stationery, one for a rhythm-and-blues duet with the President.

Your first instinct with Brother Roger, of course, is to marvel at his shamelessness. When asked about him, three White House officials, none of whom wished to be identified, replied in a single day with the same two words: ''Oh, God.'' And one top Clinton backer in Hollywood privately offers a single word: ''Nightmare.'' But when you are actually confronted with Clinton's childlike joy at his ability to take advantage of ''my brother's situation,'' as he delicately refers to the presidency, it is hard to be censorious.

So what if, after some rough patches, including life with an abusive alcoholic father, a seven-gram-a-day cocaine habit and a stint in federal prison for distributing cocaine, he's a caboose rattling along after his brother's high-speed train of an American dream? Trading on the President's name has become a First Family tradition, after all.

''In Roger's defence,'' said James Pinkerton, a Republican analyst, ''he hasn't taken a dime from the Libyans.'' Republicans are not likely to mock too much, since their favourite president was also a B-movie star. And besides, there is a compelling, cliff-hanging soap-opera quality about the adventures of the ever-expanding, and expansive, Clinton ''Roots'' saga.

''It's a dysfunctional family taken to the nth degree,'' says one top White House official with a sigh.

On this particular day, a new woman from Kansas City has popped up claiming to be the daughter of William Jefferson Blythe III, the president's father, a story that could raise doubts about whether Virginia Kelley was legally married to Blythe when she had their son, Bill.

Roger howls with laughter when he hears the news. ''Is it my sister?'' he says, his blue eyes wide. ''No way, is it? There cannot be any sister. Yeah, it's weird. It's a little sad.'' But he said he had no intention of embracing into the family any new-found offspring of the much-married travelling salesman from Hope.

''No, no, no, no, no,'' he says. ''It doesn't matter whether you believe it. You don't treat them like family because they're not a part of your family. At best, all they have is blood. But they're not family. In the South, there's a big distinction. Family is family.'' As for his mother's reaction to the bizarre news, he shrugs: ''It probably is weird for mother,'' he said. ''But you have to realise it's 50 years ago.

''Anybody should be able to handle something that happened 50 years ago, you know? If anything, all she would do now is just laugh about it. Because you see what she's gotten to. She's the greatest.''