William Daniels and his wife, Bonnie Bartlett, are getting ready to celebrate their 75th wedding anniversary, and they say their ability to “adjust” has been their secret to marital success.

The oldest living married couple in Hollywood admittedly tried to have an “open” marriage a few years after tying the knot in June 1951, but they quickly realized that was not for them.

“Well, we’ve been together actually 78 years because it was three years in college. We met at Northwestern [University]. Right, Bill? And so we’ve really been together a long time,” Bartlett, who will turn 97 next month, told Page Six via Zoom as she looked at Daniels, who turned 99 in March.

“Life is all adjustment. You’re constantly adjusting,” the “Little House on the Prairie” star continued.

“It suddenly got hot here [in Los Angeles], and it got hard to breathe and to move around. You have to kind of adjust to the heat. And that’s what life’s all about — is adjusting to whatever your circumstances are and however you move along. And certainly a marriage is full of adjustments.”

According to Bartlett, who considers herself the more “introspective” of the two, there has to be some “wiggle room” in a marriage.

We then asked Daniels, who leans into “the humor and the fun” of life, about the marriage advice he gives the countless couples who undoubtedly ask him for it.

“Don’t!” the “Boy Meets World” star quipped, as his adoring wife insisted he was just “being funny” and trying to make us “laugh.”

Laughter is another cornerstone of the pair’s enviable relationship, as Bartlett told us that her husband makes her laugh “all the time, every day.”

Despite having her own impressive IMDb page and multiple awards under her belt, the actress spent the majority of our conversation singing the actor’s praises.

While she acknowledged that part of that “automatic” response might be due to the “old-fashioned way” she was “brought up,” Bartlett also just adores Daniels — and knows his fans do, too.

“Even now when he’s forgotten so many things, I haven’t forgotten them,” she said sweetly, making sure to note that Daniels — who has trouble hearing and walking these days — is “happy.”

The duo played on-screen love interests in three major TV shows throughout their lengthy acting careers. They now sell signed memorabilia, make Cameos for fans and spend quality time with their sons: Michael Daniels, 62, and Robert Daniels, 60. (Their first son, William Daniels Jr., tragically died 24 hours after he was born.)

“We’re so lucky we have two wonderful, wonderful sons. And one of them — Michael — lives right near us, and he helps us a lot. A lot,” Bartlett marveled.

“And he has a family, and we see them. We see him and his wife, and we see all the kids, and it’s wonderful. It’s wonderful.”