Cecilia Williams, right, elicits a laugh from centenarian Thelma Kouzes in Fairfax, Va., on July 21. Williams, a friend and former exchange student from Peru, was once hosted by Kouzes and now lives with her and helps care for her. (Cheryl Diaz Meyer/For The Washington Post)

Once again, Thelma Kouzes had a full house.

Over the decades, 174 international students from 34 countries have stayed in her Fairfax home. And on Wednesday she was surrounded by friends, family and two of her former students as her great-grandson blew out the candles of her 100th birthday cake.

A Kuwaiti woman who had stayed with Kouzes in the 1990s flew in for the celebration and brought her mother. Two others from Kuwait joined in through FaceTime. And the former Peruvian student standing by all of them was the one who helped bring this international cast of family and friends together for Kouzes’s party on Wednesday.

“It’s been a good life,” said Kouzes, who also helped place more than 400 international students with American families. “I’ve met a lot of people, which I enjoy, and that’s about all I know.”

Cecilia Williams was studying at Northern Virginia Community College when she came from Peru to live with Kouzes in 1989. Back then, it was Kouzes who took her to doctor appointments, Kouzes who did her laundry, and Kouzes who cooked her meals. Now Williams, 55, says it’s her turn to take care of the woman who spent the better part of a century taking care of everyone else.

On a bulletin board next to Thelma Kouzes’s refrigerator, photos of some of the more than 150 exchange students and three refugee families she and her family hosted are posted. (Cheryl Diaz Meyer/For The Washington Post)

“I don’t have the heart to leave her,” said Williams, Kouzes’s live-in caretaker. “It’s like a gratitude I have, and forever appreciation.”

Williams, who has lived with Kouzes for the past four years, fields messages for her from around the world. Via WhatsApp, former students reach out to check in on Kouzes’s health and ask to visit when they travel to America.

Kouzes stepped into her role as a host “mom” to students after her son Jim Kouzes, now 72, heard about the American Field Service at school and asked his parents if they’d like to host Aaro, a boy from Finland. They welcomed him in 1960, and they kept inviting others.

Kouzes continued hosting students through her husband’s death in 1977 and chemotherapy for her colon cancer in 2002. “She always liked being a mother,” her son Richard Kouzes said.

Generations of families have come through the home, with former students sending their children to America to stay with Kouzes years later.

She has hosted students from Jordan, Iran and Peru, among other nations, and one of Kouzes’s “children” went on to become a Kuwaiti ambassador.

“I was ambassador, but she was my first ambassador,” said 72-year-old Abdul Hamid Al Awadhi, who spent decades as a career diplomat.

Kouzes helped him apply to college and hosted at least 10 of his brothers and sisters.

Williams watched Kouzes treat everyone coming in and out of the house like her own child. She helped them with science projects and history papers and drove them to school. She redecorated the basement bedroom in an Arabic-style design so the Kuwaiti students, and others, wouldn’t feel homesick.

These days, Williams doesn’t like to call herself a caretaker.

“I’m here because I love her, not because I’m an employee” she said.

The Kouzeses’ home always had a global focus. When her sons were young, Kouzes volunteered with the United Nations Association, and people from around the world would come over for dinner. Richard Kouzes said when he’d come home for college breaks he’d often share a room with other students, and Jim Kouzes eventually joined the Peace Corps in 1967.

The house was “a very interesting place to grow up,” Richard Kouzes said.

Now Richard Kouzes, 70, works as a nuclear physicist in Washington state, and his brother Jim is an author of more than 30 books on leadership and lives in California. He said it’s been difficult for them to live on the West Coast while his mother has required more care.

Without Williams, Richard Kouzes said, his mother would have to live in a nursing home.

“Cecilia loves my mother and visa versa,” he said.

Kouzes served as matron of honor at Williams’s wedding, and she flew to Peru to witness her son’s baptism.

When that marriage ended, Williams said Kouzes was there as her “best friend” and would attend her son’s Boy Scout banquets — and any other activity Williams couldn’t get to because of her work schedule. Williams’s parents still live in Peru.

Bryce, now 24, is in the Marines, stationed in Missouri, but still tries to FaceTime with Kouzes a few times a week.

“Mamacita in Peru and Grandma in America. . . . He always has those great memories,” Williams said. “At his birthday parties, he had the two grandmothers there.”

Kouzes’s parents immigrated from Denmark, and her husband’s family was Greek.

She said she tried to impress upon the children who lived with her that it was important to learn about different cultures and “just try to get along.”

Kouzes said she believes in “getting people acquainted across borders, across the seas.”

That message stuck with Williams. In addition to care-taking, she works as a Spanish professor at Northern Virginia Community College and a volunteer interpreter for various nonprofit immigrant groups.

Williams also helps people prepare for their naturalization exams and serves on the Virginia Latino Advisory Board for Gov. Terry McAuliffe (D).

Kouzes doesn’t talk as much as she used to. She passes the days playing cards and doing crosswords. Each morning, Williams and Kouzes share the newspaper, poring over every section except for sports. They watch “Jeopardy” and “Wheel of Fortune” every night, and sometimes Kouzes still yells out the answers.

Throughout the day, Williams doesn’t let Kouzes forget the adventures she had: She reminds her she once hiked Machu Picchu, toured the pyramids and walked the Great Wall of China — all in high heels.

Three years ago, a blood clot in her leg left her unable to walk, and now Kouzes uses a wheelchair. Richard Kouzes said his mother doesn’t take medication because she doesn’t believe in it.

Kouzes said she still likes to dance — she met her future husband on the dance floor — so Williams blasts “YMCA” from her cellphone and does the dance motions in the living room as Kouzes smiles.

Williams used to bring Kouzes to her college parties to dance.

“My feet don’t work, but other than that I like it,” Kouzes said.

Williams manages the four other caretakers, not counting the nurses through hospice care who bathe her and check her vitals every other day.

Only one other caretaker is fluent in English, but Williams said the language barrier doesn’t bother her. When she screens caretakers, she tells them she requires three things for Kouzes: “Hug her, kiss her, tell her multiple times ‘you’re beautiful.’ ”

Williams reminds hospice nurses when they need more diapers, gloves and bed liners.

A “Do Not Resuscitate” form hangs on the refrigerator, but Williams tries to ignore that. Around the corner, there’s corkboard layered with dozens of photos of Kouzes’s students.

On a recent day, Williams leaned over Kouzes’s wheelchair and spoke loudly into her ear so Kouzes could hear her: “I love you,” she said.

“Thank you,” Kouzes said.

Williams laughed and asked, “Do you love me?”

“Yes, indeed,” Kouzes said with a smile.

“How much?” Williams asked.

“A lot,” Kouzes said, and she kissed Williams’s cheek, leaving a red lipstick mark behind.