The 53-year-old reality star said as much this week while sharing a photo of the 24-year-old British singer embracing Gigi.
"Summer Loving....... #Family," she captioned the picture on Instagram.
The black and white snapshot shows a shirtless Zayn giving Gigi a bear hug. The singer rests his chin atop Gigi's head as the 22-year-old model smiles and returns his embrace.
"Happiness is seeing your kids happy and realizing they turned out to be really good and genuine people," she captioned a different photo of the couple.
Gigi and Zayn were first linked in November 2015, and made their red carpet debut as a couple at the 2016 Met Gala. Zayn told the Evening Standard in June that he and Gigi are a "normal" couple despite their fame.
"I can understand how it can look, that you've got these two people in a 'power couple,'" the former One Direction singer said. "That's not something I want to be a part of. I'm with her because I like her."
"When we come home, we don't really talk about that [expletive]," he added. "We just spend time together as a normal couple, cook food, watch TV, have a laugh."
Gigi is known for her modeling work with Tommy Hilfiger, and will return with sister Bella to walk the 2017 Victoria's Secret Fashion Show. Zayn released his debut solo album, Mind of Mine, in March 2016.