How Chris Pratt Proposed to Katherine Schwarzenegger (Exclusive)

Chris Pratt made sure to make his proposal to Katherine Schwarzenegger a memorable one. 

Chris Pratt made sure to make his proposal to Katherine Schwarzenegger a memorable one. 

A source tells ET that the 39-year-old actor prepared a romantic speech for 29-year-old Schwarzenegger when he popped the question. Pratt shared that the two got engaged on Instagram on Sunday night with a sweet picture of himself kissing his new fiancee on the head as she gazes at her engagement ring.

“Chris was very sweet when he proposed to Katherine, as he had a romantic speech prepared explaining how important she was to him," the source says. "Katherine complements Chris and is very good for him."

The source also notes that Schwarzenegger and Pratt's ex-wife, Anna Faris, get along great, and that Schwarzenegger loves the exes' 6-year-old son, Jack.

"Anna and Katherine have met a few times and get along and that was very important to Chris," the source says. "Anna is excited for Chris and Katherine and above all is happy Chris is with someone who loves Jack like their own. The couple got engaged quick but everyone around them saw it coming. They really are a great couple that have a solid foundation. Chris had the approval of the family and everyone is excited for their union.”

Indeed, Faris congratulated Pratt and Schwarzenegger on their engagement, commenting on Instagram, "I'm so happy for you both!! Congratulations!"

Schwarzenegger's mother, Maria Shriver, also congratulated her daughter and future son-in-law.

"Congratulations to two loving, kind, caring, thoughtful, spiritual people," Shriver wrote. "We are so happy for you. You are blessed, as is everyone who knows you. Yes, let's go." 

Pratt and Schwarzenegger were first spotted together last June and only made their relationship Instagram official last month.

Last July, a source told ET that the two's relationship got serious quickly.

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

On his Instagram post about his engagement, the Jurassic World star said he was so "thrilled" to be taking the next step in their relationship.

"Sweet Katherine, so happy you said yes!" Pratt wrote.  I’m thrilled to be marrying you. Proud to live boldly in faith with you. Here we go! ♥️"

Schwarzenegger later shared the same picture on Instagram, writing, "My sweet love. Wouldn’t want to live this life with anyone but you ♥️?."

Kathryn Money, Vice President of Strategy and Merchandising for Brilliant Earth, tells ET that Schwarzenegger's engagement ring appears to feature an estimated 6-7 carat diamond. The designer of Schwarzenegger's engagement ring -- which appears to be an elongated cushion cut or oval shaped diamond in a delicate solitaire setting -- has not been disclosed.

According to Money, “depending on the quality and specific characteristics of the center diamond, we estimate the cost of the ring at approximately $150,000-250,000 or more.” 

For more on the couple, watch the video below: