Earlier this month, Elverum and his daughter moved from Anacortes, Washington to live with Williams and Matilda in Brooklyn.
"I never gave up on love," Williams told Vanity Fair. "I always say to Matilda, 'Your dad loved me before anybody thought I was talented, or pretty, or had nice clothes.'"
"Obviously I've never once in my life talked about a relationship," she said, "But Phil isn't anyone else. And that's worth something. Ultimately the way he loves me is the way I want to live my life on the whole. I work to be free inside of the moment. I parent to let Matilda feel free to be herself, and I am finally loved by someone who makes me feel free."
It is unclear how long Williams and Elverum have been together. Earlier this year, she was romantically linked to New York financial consultant Andrew Youmans.
In March, Williams' bestie and fellow Dawson's Creek alum Busy Philipps posted on Instagram a photo from the March For Our Lives rally in Los Angeles: It shows her with her husband and their two daughters and Elverum, holding a protest sign.