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Kendall Jenner‘s life has been documented by cameras since she was a preteen, but now the model is trying to keep one part of it away from the spotlight – her relationship with Jordan Clarkson.

“They’re both more private,” explains a source close to Jenner, who celebrated the Fourth of July with the Lakers’ player at Bootsy Bellows’ Malibu pop-up party. “When they’re out in public, they are never all over each other.”

Indeed, the pair kept any PDA to a minimum at the Los Angeles hotspot’s “Red, White and Bootsy” bash, but the source says Jenner and Clarkson’s “relationship has been getting stronger over the last couple of months.”

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“They’re very openly affectionate when they’re comfortable … with friends or alone on a date,” says the source. “They enjoy low-key dates like quiet dinners where they won’t be bothered.”

And though another insider recently told PEOPLE their relationship wasn’t completely “serious” yet, the source adds the duo – who have been linked since March and also attended Coachella together – are definitely heating up.

“They really like each other and Jordan is super into Kendall,” says the source.

Keeping Up with the Kardashians airs Sundays (9 p.m. ET) on E!