A source tells ET that the couple has shared a strong connection ever since they began seeing each other.
"The moment Chris and Katherine started dating, everything fell into place and they seemed inseparable," the source says. "They just love each other's company and have so much in common."
The source continues, "They spend a great deal of time together. Chris and Katherine have the full support of her family and Maria [Shriver] feels they are a match made in heaven."
Pratt, 39, and Schwarzenegger, 28, were first photographed together in June, and she has since met the actor's 5-year-old son, Jack, with his ex, Anna Faris.
“Chris is dedicated to co-parenting and he's a huge support to Anna," the source says. "Their break wasn't easy and they both want to be the best parents they can be. Chris is dedicated to juggling career, family and Katherine.”