DAVE THOMAS WASN’T CRAZY ABOUT the idea of searching for his birth father. The beefy, grand-fatherly founder of the popular Wendy’s fast-food chain, who was born out of wedlock and adopted in infancy, had sought out his birth mother’s family in Atlantic City 40 years ago, when he was 21. His mother, it turned out, had died, but he met her family and didn’t feel any particular closeness to them. With no leads to his father, Thomas didn’t see much point in trying to track him down.

Five years ago, Thomas’s eldest child, Pam, now 38, look up the search herself—with her father’s blessing. After a few false starts, she found the family in Philadelphia and learned that Thomas’s father, by then dead, had married and fathered a legitimate son, a brilliant college professor who graduated from MIT—and who wanted nothing to do with his half brother. “He didn’t want his mother to know that his father had a little one-night deal,” Dave says. “He might be very, very smart, but he doesn’t have much common sense.”

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There’s still the sling of rejection in his voice, and it comes as little surprise that Thomas’s belief in the sanctity of family approaches religious fervor. He is so committed to the ideal of a loving home for every child that in 1992 he set up the Dave Thomas Foundation for Adoption to encourage the practice. He also wants to do away with the stigma surrounding it. “You’d be surprised the people who were adopted who don’t want to talk about it,” says Thomas in his folksy, Midwestern vernacular. “It’s hard for people who have a mother and father to understand. Adoption was like the plague.”

Sometimes it’s hard for Thomas’s five children to understand why he promotes adoption with such zeal, since his own experience was not a good one. Not only did Thomas’s adoptive father, Rex, a construction worker, withhold affection (“He fed me, and if I got out of line he’d whip me”), but Thomas, who spends more than half his lime on the road, has proved to be less than a model parent himself. “He doesn’t seem to know how to be with us,” says Thomas’s son, Ken, 37. “For him, home is a nice place to visit, but he doesn’t want to live there.” Thomas makes no apologies. “How can I explain? I like to be around them, but I couldn’t do it too much because it would bother me. We’d bug each other.”

Growing up in western Michigan, Thomas saw his adoptive mother, Auleva, die of rheumatic fever when he was 5. His love of food grew later, during all those limes he and Rex ate-out in greasy spoons. “I thought if I owned a restaurant, I could eat all I wanted for free,” he says. “What could be better than that?”

Rex remarried three times after Auleva died, moving his family from one Midwestern city to another for his work. By the time Dave was 15, he had lived in a dozen different places. “I never really had a chance to get to know anyone, and I never fell I belonged,” he says. His sense of being an outsider deepened when Auleva’s mother, Minnie Sinclair, told the 13-year-old Thomas that he had been adopted. “It really hurt that nobody told me before,” he recalls, “it is a terrible feeling to know my natural mother didn’t want me.”

When Rex moved the family to Fort Wayne, Ind., in 1947, Thomas was hired as a busboy at the Hobby House restaurant. By the end of the year, he had quit school and moved out of the family trailer and into the YMCA. After a two-year stint in the Army, Thomas returned to the Hobby House in 1953 as a $35-a-week short-order cook. To the new 18-year-old waitress, Lorraine Buskirk, he was a local hero. They married seven months later and had four children—Pam, Ken, Molly, 35, and Wendy, 32—in six years. Another daughter, Lori, was born in 1967.

In 1962 he moved the family to Columbus, Ohio, where he became part owner of four foundering Kentucky Fried Chicken outlets. Not only did he turn them into lucrative franchises, but he later came up with the idea of the revolving KFC sign.

Eventually, Thomas and KFC’s Colonel Sanders reached a critical philosophical impasse over the proper method of frying chicken. “He wanted it ladled out of the oil by hand,” says Thomas. “I believed in dumping. It was faster and got the chicken out of the grease better.” In 1968, Thomas decided to sell his share of the KFC franchises for more than $1 million in cash and stock. He used some of the money to start up his own place, specializing in the meal he loved most—fresh-to-order hamburgers.

Thomas knew he needed a unique logo to draw diners. “I think a little girl’s image is the greatest—wholesome and cute,” he says. “Wendy was 8 at the time and had red hair, freckles and buck teeth. Molly was a couple of years older.” Finally, Wendy’s stick-out pigtails won out. Thomas opened his first Wendy’s Old Fashioned Hamburgers in downtown Columbus in November 1969. Within six weeks the place was making a profit. Wendy’s now boasts more than 4,000 restaurants in 29 countries.

Hawking his hamburgers, fries and salads on TV commercials, Thomas has earned international recognition—as well as four homes and lots of grown-up toys, including a golf course in South Carolina. But it has all come at a price. “He was always overtired,” says Pam. “He really didn’t know how to treat kids, didn’t know how to go to a baseball game. My mom really held it together.”

Still, Thomas, who admits to changing maybe a couple of diapers in his entire life (“and those were only wet”), has won his family’s respect. “He didn’t have anything as a kid,” says Wendy. “He still won’t let anyone see his feet, which are all screwed up because he never had proper-fitting shoes. But Dad is a very giving guy. He’s earned it, and he shares it.”

In the late 1980s, the National Council for Adoption asked Thomas for his support, and in 1990 President Bush sought his help in publicizing the plight of those who are least likely to be adopted: the handicapped, older children and siblings. Wendy’s corporate adoption program, which Thomas started in 1990, helps Wendy’s employees adopt children by paying some of their medical, legal and counseling costs. Says Thomas: “People ask me, ‘What about gay adoptions? Interracial? Single parent?’ I say, ‘Hey, fine, as long as it works for the child and the family is responsible.’ My big stand is this: Every child deserves a home and love. Period.”

Well, maybe semicolon; there’s also an education. Thomas regularly talks to groups of teenagers, urging them to stay in school. “The kids would look at me and say, ‘Here’s this guy who’s really successful, and he dropped out. Why don’t you practice what you preach?’ ” So he got his G.E.D. and graduated from Coconut Creek High School in Florida this spring, and in May he and Lorraine went to the senior prom. His schoolmates voted him Most Likely to Succeed. It was a hard-won honor that Thomas wants all children to get a crack at. “Even though my adoptive situation wasn’t perfect, it was far better than an orphanage,” he says. “I’ll try to help any kid get a home.”