A source tells PEOPLE the newly engaged couple made a point of including Pratt’s 6-year-old son with ex-wife Anna Faris into their outings as they got to know each other.
“Instead of mostly enjoying solo, romantic dates, Chris’ son from early on was a very big part of their dating life,” says the source.
Schwarzenegger, 29, enjoyed the time she spent with father and son, adds the insider.
“Katherine never minded that her dates with Chris many times involved a kid activity, like a matinee movie, or going to Disneyland,” says the source. “Katherine is like a big kid and loves doing activities with Jack. She loves that Chris is a dad.”
While Schwarzenegger does not have children of her own, witnessing the Guardians of the Galaxy, 39, bond with his young son factored into her decision to marry the star, says the source.
“Seeing Chris with Jack made Katherine positive from early on that Chris is ‘the one,'” adds the source.
And their engagement, which the couple announced on Monday, couldn’t have come at a better time.
“For someone on the outside, it might seem their engagement came too quickly,” the source told PEOPLE earlier. “But for everyone close to them, it feels like they have been dating much longer than they actually have.”
The pair hit it off after Schwarzenegger’s mother, Maria Shriver, introduced the two.
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“They never had a typical relationship. It very much helped that Chris already knew Maria,” the insider said. “They didn’t have to take things slowly because they were getting to know each other’s families. Katherine’s family instantly treated Chris like a family member.”
Pratt, who used to live in the Hollywood Hills with Faris, 42, recently joined his fiancée in west Los Angeles.
In his divorce settlement with Faris, the exes agreed to live no further than five miles apart from each other until Jack completed the sixth grade. The Mom actress, who’s dating cinematographer Michael Barrett, also now lives in west Los Angeles.
For more about Pratt and Schwarzenegger, pick up this week’s issue of PEOPLE, on newsstands now.