Veronica Berti and Andrea Bocelli in Rome, Italy in October 2024. PHOTO: DANIELE VENTURELLI/WIREIMAGE

After two decades together, Andrea Bocelli and Veronica Berti know how to keep their love alive.

The secret to their love is quite simple, the Italian tenor says, and requires a strong foundation.

“I think that at the foundation of every relationship that can work over time, it’s a matter of chemistry,” Andrea, 66, tells PEOPLE exclusively.

He adds, “If there’s no chemistry, it’s very difficult to live together the way we do.”

In addition to chemistry as a strong foundation, Andrea believes that marriage is an “ongoing process.”

Amos Bocelli, Virginia Bocelli, Andrea Bocelli, Matteo Bocelli and Veronica Berti in Italy in July 2024.VITTORIO ZUNINO CELOTTO/GETTY

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“Both people must make the other person happy. So we work constantly to make each other happy,” Andrea says.

He adds, “Love is like a fireplace. We must feed, renew wood and we have to keep the flame alive.”

In March 2023, Andrea and Veronica opened up to PEOPLE about their film The Journey: A Music Special from Andrea Bocelli, which saw the couple travel through the beautiful landscapes of Italy. At the time, Veronica revealed what she thought was the secret to their unbreakable bond.

“We’ve lived together almost 22 years now, and, at least at the beginning, spent 24 hours a day [together],” Veronica said at the time. “So, either you love each other or you kill each other, and luckily we were able to do it.”

“Sometimes we don’t necessarily agree on the path, but we always agree on the aim. We rely on each other,” she continued. “What I love about him is his determination and how fast he can make a decision. Indecision makes me very nervous.”

Andrea Bocelli and Veronica Berti. LAURA LEZZA/GETTY
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The couple met in 2002 when Andrea serenaded her with a special aria and they dated for more than a decade before marrying in 2014. In 2012. the couple welcomed a daughter, Virginia, 12. Veronica is also stepmom to Andrea’s two sons from a previous marriage, Amos and Matteo.

In a recent documentary titled Andrea Bocelli: Because I Believe, which premiered at the Toronto International Film Festival on Saturday, Sept. 7, Veronica opened up about her feelings toward Andrea’s close interactions with women onstage.

“People ask me, ‘Aren’t you jealous?’ No. I’m not,” Veronica said of her husband in the documentary.

“It would be silly. If it’s a nice person, someone pleasant, whom you can sing about love with and be inspired from, all the better,” she continued, noting that she’s “confident enough not to be affected by it.”