Jessica Simpson was on to something when she named her debut album Sweet Kisses in 1999.
More than 16 year later, the singer-turned-fashion-mogul says that's what keeps the spark alive in her relationship with husband Eric Johnson.
"I think the secret to a beautiful, loving marriage is just making out!" Simpson, 35, tells PEOPLE. "Don't forget to kiss. It's more intimate sometimes for a lot of people and if you forget that, you forget why you fell in love in the first place. It always begins with a kiss."
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By the looks of their steamy and silly social media, Simpson and Johnson, 36, make plenty of time for each other, but bonding with their children – Maxwell Drew, 3, and Ace Knute, 2 – is also a top priority. And hitting the road can be a great way to make that happen.
"Growing up, some of my best memories are road trips," says Simpson, who was recently named Budget Car Rental's newest brand ambassador. "Somehow I always got lucky on the way to my nanny's house and I would get a lotto ticket and I would win. Even if it's a dollar, I still would always win!"
The fashion designer, who stars in Budget's new ad campaign, adds: "Now when we go on road trips I'm always like, 'Hey, Eric. We have to buy a lotto ticket! I bet we'll win!'"
For more on Jessica Simpson's life as a mogul mom, pick up the latest issue of PEOPLE, on newsstands Friday.
Time spent on the road can often be the most fun – especially with two kids under four.
"My kids rarely fall asleep in the car. They never did, even as babies. They like to just chatter and talk or ... cry," Simpson says. "Sometimes we have to turn around and go back home and then start back over. But they're always very chill in the car unless they're like bantering back and forth. And then me and Eric just have to tune them out. Just let them talk back and forth and get through it. They're brother and sister."
Though Simpson maintains a hectic schedule nowadays, she says her family role is the best job.
"Family is always work, but it's the best kind of work you can possibly do," the proud mom says. "It's the best kind of togetherness and realness you can have in your life."