Casamigos Tequila founder Rande Gerber and supermodel Cindy Crawford have been married since 1998 -- an impressive 17 years. In the wake of Hollywood's latest big split (unfortunately we're talking about Ben Affleck and Jennifer Garner, of course), a celebrity marriage with that kind of lasting power becomes all the more impressive.
WATCH: Rande Gerber Says He Plans to 'Buy a Shotgun' As Model Daughter Kaia Gets More Famous
But Gerber says the secret is one word: friendship.
"We started as friends and we remained friends," he tells ET. "You have to just keep that friendship and fun in the relationship."
Gerber says he and Cindy -- who have two children, Presley and Kaia -- make sure to find time for one another. That includes family vacations to their house in Mexico -- a property they share with Gerber's longtime pal, George Clooney.
Gerber says both he and Clooney got lucky with their ladies, Cindy and Amal. "We're very fortunate," he says.
WATCH: George Clooney Reveals Why He Fell in Love With Amal