Hawn and Russell, who both had children from previous marriages, got together in 1983 and have raised their kids in a blended family ever since. Hawn shared daughter Kate Hudson and son Oliver Hudson with her ex, Bill Hudson. Russell also had a son, Boston Russell.

Three years after they got together, Hawn and Russell welcomed son, Wyatt Russell.

Speaking to PEOPLE in April, Hawn said Russell, 69, has always made her feel beautiful in their 37 years together.

“The other night we were going to go have dinner. He looks at me and goes, ‘You’re unbelievable,’” Hawn recalled. “‘He said I cannot believe how [beautiful] you look.’ He really appreciates that.”

Her daughter Kate added that living up to Hawn and Russell’s relationship “is really the goal.”

“Just the fact that they’ve been able to maintain a unit for all of us, in times of turmoil, they really are the center of all of our lives,” Hudson said.

He also shared a photo of him and sister Kate posing together when they were children.

On Sunday, Oliver also shared a tribute to his stepfather in his own Father’s Day Instagram post, which featured an old family photo of Hawn, Russell and the children.

“Mr. Russell, AKA PA.. you swooped in and completed our family. I was 6.. fearful and uncertain, and you taught me confidence and independence.. ❤️,” he began in the post.

Hudson continued, adding notes for his biological father and for his father-in-law: “Mr Hudson, AKA DAD.. you gave me life, you gave me humor, you gave me the ocean, you gave me depth.. ❤️Mr Bartlett, AKA FATHER IN-LAW.. you gave me a limo, a 6 pack of Miller Lite and a joint the first night I met you.. ❤️ HAPPY FATHERS DAY!!! #mythreedads.”

He also shared a photo of him and sister Kate posing together when they were children.