Nursing home administrator Myles Nienstadt has already lost his father to Alzheimer's. Now he is working in the same facility where his mother is dealing with her own battle. (Drescher Films, Inc)

For a recent session on the Chinese zodiac, the residents of Birmingham Green, an assisted-living facility, sat in a circle and tried to recall what year they were born. Some shook their heads sheepishly, others answered easily — Caroline, born in 1927, was a tiger. Herbert, born in 1953, was a dragon.

Jean Sullivan, a 90-year-old doctor with silver hair neatly cut below her chin, stared ahead and said nothing. Then, from the doorway, Myles Nienstadt, the long-term care facility’s director of information resources, said softly, “1925. She was born in March of ’25.”

He would know. Because he’s not just an administrator at the Manassas facility — he’s also her son.

He remembers “Doctor Jean” as a vibrant globe-trotting divorced mother of four. In the late 1950s she was a Quaker medical missionary in South Korea; in the 1960s she supported the antiwar priests Daniel and Philip Berrigan; in the 1970s she piled the kids into a converted bus to drive across the country; and starting in 1986 she ran a health clinic in rural Kentucky. That ended in 2006, when Sullivan got lost overnight in the mountains while out on a house call; a televised search helped find her, and she was diagnosed with dementia. She moved into the McLean home of Nienstadt and his wife and children.

Nienstadt, an executive with a nonprofit group, had already become interested in long-term care after seeing his father succumb to Alzheimer’s in a large, impersonal facility. Now, as he took his mother each day to an Alzheimer’s day care program, he thought about starting one himself. He had done some consulting for Birmingham Green, and in 2012 when his mother began to need more than he could provide at home, he moved her there.

Myles Nienstadt, director of information resources at Birmingham Green, sits next to his mother, Jean Sullivan, a resident at the assisted-living facility (Matt McClain/The Washington Post)

At the same time the facility’s chief executive, David Rumford, had a suggestion: “Come train here as a nursing home administrator.” He accepted, and now works there full-time, helping the facility go digital.

Having an employee work at the same place as a relative is not uncommon in small communities with only one or two care facilities, Rumford said. Birmingham Green has had several over the years. “It’s a pride thing — that ‘this place is good enough, I could bring my mother here.’ ”

Compared with other residents, Nienstadt said, his mother has “the distinct benefit of seeing a familiar face from her past, basically day in and day out.” Like other family members of assisted-living residents, he attends regular meetings to go over what has changed in the last 90 days. But unlike his visits to his father — once a week, at night or on weekends, his interactions with his mother are more casual and more nuanced.

“I get to observe her very naturally. By just being here and out and about, I can see where she is at any given time,” he said. “I can say, ‘Hi there, how’s it going?’ I can do that quick checking in.”

And the guilt many have about placing their loved ones in facilities? “If I can only stay 10 minutes or 15 minutes, I’m comfortable with that. I’ve never had any feeling of guilt about the time not taken.”

Out on the floor, Nienstadt helps fill in the disappearing jigsaw pieces of her life. On her 90th birthday he showed old home movies to the residents — the active woman scrambling through a forest, the young mom cuddling her babies — the mother he remembered.

He also advocates for her. “I’ve been watching him stand up for how his mother would want to be taken care of,” said Tina Burhans-Robinson, director of activities for assisted living. That means no drugs or heroic measures to keep her alive if they decrease her quality of life. “He says, ‘We’re not here to prolong her life, we’re just here to make her comfortable.’ ”

A baby photograph and a more recent photo of Jean Sullivan in the office of her son, Myles Nienstadt. (Matt McClain/The Washington Post)

After the zodiac session on Monday, Nienstadt sat beside Sullivan and took her hand. He has a mild, gentle aura, a trim beard that matches his sandy-brown hair, a face she has known for 56 years.

“Hi Mom, how are you doing? Anything new today?”

Her head turned in his direction, the expression behind her glasses inscrutable.

“Have you read the newspaper today?”

“Uh huh,” she said in a wavering voice.

“What’s up? Same old, same old?”

“Same old, same old.”

It’s a question he asks every day, less of an earnest query than a gauge of her condition. “She says yes, though I know for a fact that she hasn’t — but if she ever said no, I’d know something had changed,” he said. She was always a voracious reader and she still has a 2012 copy of Scientific American in her room. But these days she’ll pick up the newspaper, maybe read out a word from a headline, then put it down.

That is the trajectory of Alzheimer’s. The caregiver must constantly adjust, learning with each interaction what is still possible and what is no longer possible. Once someone is placed in a facility, interactions with family members can become less frequent, limited by work schedules, distance, and sometimes by the sharp pain of watching a beloved relative or friend fade away.

At first, having his mom hanging around Nienstadt’s job was almost too much . While Sullivan was still lucid enough to know where his office was, she used to knock on the door. Often. Oh, I don’t want to bother you, I just want to check on how things are going. It was, he said, like having a teenager or a 5-year-old along at work. “She was too aware that I was there, she was knocking a little too much.”

Now, aside from a few patterned conversations such as the one about the newspaper, their interactions are wordless. She drums her fingers on a table; he drums his in response. Sometime last fall she stopped saying his name, but she remains aware of him. While he was away on a two-week family vacation last summer, staff members told him she acted differently. She seemed less comfortable. She scratched at herself until she opened up a wound.

His work at the facility has made him more sensitive as a family member, Burhans-Robinson said. “Some people go straight to their mom and ignore everyone else,” she said. “He treats [other residents] with the same respect he treats her. It’s comforting. You have a lot of residents who their relatives don’t visit very often, and he isn’t dismissive of them. They’ll stop and say something to him, and he’ll crack jokes.”

But for him, Sullivan is the special one. Sitting in her room, on her single bed, Nienstadt pointed to artifacts he has placed nearby to jog her memory: a smiling black-and-white photo of Sullivan as a girl in California, perched on the hood of a Model T with her arms outstretched, watercolors she painted of cranes and a hummingbird, and a letter from a childhood friend.

They provide comfort for Nienstadt as well. “I do wander in every now and then to just take a look. I don’t dwell too much,” he said. “But in the last few weeks because her presence has been more in here, on occasion when I’m in here I just sit and check in on her space.”

Since he sees her every day, he catches the tiny signs of decline. The “tomboy” who refused a walker and waved away canes now reaches for his hand as they walk down the hall.

Hanging in the air is the knowledge that someday this dual life will end. One day she won’t be there, and Nienstadt will be just a man going to his job each day, albeit a job colored by the years of having his mother close by. For now, he pops up to the common area from his office downstairs. Seeing him glance around, a few residents point at Sullivan. Sometimes, some of them think he is their son.

And he is fine with that.