In a 2018 letter for their charitable foundation, Bill and Melinda Gates answered some questions they get often.
Melinda answered the question "What happens when the two of you disagree?" by saying she and her husband agreed on basic values.
Relationship experts (and long-married people) agree that sharing core values is an important part of a successful relationship.
Melinda and Bill Gates are one of the world's most influential power couples — and one of the ways they've worked to maintain their relationship is by focusing on what they have in common.
Melinda started her answer with a joke: "We never disagree. Just kidding." She then said that Bill never gets asked that question (and that journalists and women philanthropists are the ones who ask Melinda). After diving into the topic, she stated that there are several things going in their favor, with one particularly sticking out: "We agree on basic values."
She wrote about a wedding gift they received from Bill's parents that symbolized this idea. It was a sculpture of two birds side by side staring into the distance.
"It's still in front of our house," Melinda said. "I think of it all the time, because fundamentally we're looking in the same direction."
RELATED: Take a look at the world's oldest living couple:
Melinda has said that a way they put their shared values into practice is by having equal household responsibilities. For example, Melinda and Bill wash dishes together every night. Melinda previously told Business Insider that splitting family chores has fostered an even stronger bond for the couple.
Another key strategy to their successful marriage is divvying up childcare. Gates is adamant about driving their kids to school. Because of this, Melinda says other dads in the community have modeled this behavior.
"A few weeks into the school year, some other moms sidled up to me and they said, 'Hey, do you see what's changing in the classroom?'" Melinda said. She added, "I'm seeing more dads dropping off kids. They're like, 'Yeah, we went home and we told our husbands, if Bill Gates, who's the CEO of Microsoft, right now can drive his kid to school, so can you!'"
Relationship experts would agree with Melinda's assessment of what makes a marriage work.
Peter Pearson, a couples psychologist who is the cofounder (along with his wife) of the Couples Institute, previously told Business Insider that finding someone who shared the same core values as you was the "holy grail" of relationships.
Values are different from interests, Pearson said. If you, say, love going to concerts and your partner doesn't, you can probably find a friend to go with you instead.
But if you're obsessed with earning more money and power and your partner is OK where he or she is — a situation Pearson has seen before — you may run into problems.
Karl Pillemer, a professor of human development at Cornell University, spoke with a series of older Americans for his book "30 Lessons for Loving" and came to much the same conclusion about the importance of shared values.
One 86-year-old man told Pillemer that it's important to find out from your partner: "What do they care about? How do they think about the world? What matters to them?"
Pillemer's interviewees recommended having an explicit discussion about core values with your partner before getting married, or deciding to be together long term. You'll want to cover values around children, money, and religion — and whatever else is important to you.
An 80-year-old man put it in very frank terms: "If you have divergent personalities and ideas of what's right and wrong, and what you want to do and what you don't want to do right at the very beginning, well, it's not going to get better. It's going to go downhill."
More from Business Insider:
50 stores you once loved that don't exist anymore
The entrepreneur's ultimate guide to partnering with Amazon so you can make a boatload of money with fewer risks
Scientists have identified a series of warning signs that predict divorce. Here's relationship experts' best advice on what to look out for.