A 30-year search for a lost American cousin ended in Union Station yesterday afternoon when London's Julia Proops hugged Willard Rieger of Fairfax.

But for a faded family photograph - and the interest and curiosity of a total stranger from the District of Columbia-Proops and Rieger might never have met.

The photo is of Rieger at the age of 3, and when the Bristish-born Mrs. Proops came across it 30 years ago among her grandmother's possessions, she said, "I decided to look for him."

She wrote "hundreds of letters to everyone except the president." When she came to the United States last summer, she continued the search. Seh called all the Riegers in New York City and wrote all 23 Riegers in the Philadelphia phone book, without success.

While in LaJolla, Calif, last October, she told her story to a local newspaper setting in motion a bizarre sequence of events that finally put her in touch with her second cousin.

"I never give up," said Proops, who steadfastly refused to reveal her age saying only she is older than the 51-year-old Rieger, a planning officer for the Naval Air Systems Command here. Chatting excitedly-she in her clipped British accent and he in the rugged speech of his native Bronx-the two immediately began catching up on family history and explaining how they found each other.

Proops' story in the California paper caught the attention three months later of Gladsy Sterns, a District resident who teaches in Arlington.

The article told how Proops' grandmother had brought the family to Philadelphia and how the grandmother and all her daughters-but one-had eventually returned to England. The name and picture of Rieger accompainied the story, but Proops was quoted as saying she had no idea whether her cousin was even still alive.

"I thought someone living in Philadelphia might have come to Washington to get a job, so I just picked up the phone book and looked up the name," Sterns said yesterday. She found the name right away but "waited about a week to call because I was kind of leery."

After talking to Sterns, the Riegers found the same picture she had described from the article. The Riegers called the newspaper, which put them in touch with Proops.

Rieger said the family's own interest in its "roots" was sparked when their daughter had to do a genealogy chart for school "and my mother's mother was the farthest we could trace it back."

Proops, who worked as a secretary for the House of Lords, plans to return to London after a brief vist with the Riegers, and they are making plans to visit her in England. The couple was there for a week in August, about the time Willard Rieger's cousin arrived in LaJolla. CAPTION: Picture, Willard Rieger of Fairfax hugs English cousin Julia Proops at Union Station. By Fred Sweets-The Washington Post