Chris Pratt and Katherine Schwarzenegger's relationship has become 'serious quickly'

Looks like Chris Pratt and Katherine Schwarzenegger's romance is heating up fast!

Just a few weeks after the newfound couple were spotted out and about together, a source now tells ET that the two have "gotten serious, quickly."

"[They] went from casually dating to spending much more time together," the source says. "Chris and Katherine have introduced one another to their family and friends, and have been almost inseparable when they are free."

According to our source, Schwarzenegger (the daughter of Arnold Schwarzenegger and Maria Shriver) has even "spent quality time" with Pratt's 5-year-old son, Jack, whom he shares with his ex-wife, Anna Faris.

"That was a big step for Chris," the source adds. "Until he knew it was more than just casual, he wasn't introducing Jack to anyone. Chris and Katherine are very happy together."

Pratt, 39, and Schwarzenegger, 28, were first seen together in June, on a casual picnic in Santa Barbara, California. Since then, the two haven't been shy about showing their affection toward one another in public.

Over the weekend, photographers snapped pics of the actor and his lady locking lips while enjoying some ice cream in Los Angeles.

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Chris Pratt and his son Jack together
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Chris Pratt and his son Jack together
ANAHEIM, CA - FEBRUARY 24: Actor Chris Pratt and son Jack attend Monster Jam Celebrity Event at Angel Stadium on February 24, 2018 in Anaheim, California. (Photo by Ari Perilstein/Getty Images for Feld Entertainment)
ANAHEIM, CA - FEBRUARY 24: Actor Chris Pratt and his son Jack attends Monster Jam Celebrity Event at Angel Stadium on February 24, 2018 in Anaheim, California. (Photo by Ari Perilstein/Getty Images for Feld Entertainment)
ANAHEIM, CA - FEBRUARY 24: Actor Chris Pratt and son Jack attend Monster Jam Celebrity Event at Angel Stadium on February 24, 2018 in Anaheim, California. (Photo by Ari Perilstein/Getty Images for Feld Entertainment)
LOS ANGELES, CA - DECEMBER 06: Actor Chris Pratt and son Jack Pratt attend a basketball game between the Los Angeles Clippers and the Minnesota Timberwolves at Staples Center on December 6, 2017 in Los Angeles, California. (Photo by Allen Berezovsky/Getty Images)
LOS ANGELES, CA - DECEMBER 06: Actor Chris Pratt and son Jack Pratt attend a basketball game between the Los Angeles Clippers and the Minnesota Timberwolves at Staples Center on December 6, 2017 in Los Angeles, California. (Photo by Allen Berezovsky/Getty Images)
HOLLYWOOD, CA - APRIL 21: Actor Chris Pratt and son Jack Pratt attend the ceremony honoring Chris Pratt with a star on the Hollywood Walk of Fame on April 21, 2017 in Hollywood, California. (Photo by Axelle/Bauer-Griffin/FilmMagic)
HOLLYWOOD, CA - APRIL 21: Actor Chris Pratt and son Jack Pratt attend the ceremony honoring Chris Pratt with a star on the Hollywood Walk of Fame on April 21, 2017 in Hollywood, California. (Photo by Axelle/Bauer-Griffin/FilmMagic)
HOLLYWOOD, CA - APRIL 21: Anna Faris, Jack Pratt and Chris Pratt attend a Ceremony Honoring Chris Pratt With Star On The Hollywood Walk Of Fame on April 21, 2017 in Hollywood, California. (Photo by Tommaso Boddi/WireImage)
SEATTLE, WA - JULY 30: Actor Chris Pratt and son Jack Pratt ride in the Seafair Torchlight Parade Grand Marshal vehicle on July 30, 2016 in Seattle, Washington. (Photo by Suzi Pratt/WireImage)
SEATTLE, WA - JULY 30: Actor Chris Pratt and son Jack Pratt ride in the Seafair Torchlight Parade Grand Marshal vehicle on July 30, 2016 in Seattle, Washington. (Photo by Suzi Pratt/WireImage)
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