The 39-year-old actor took to social media on Tuesday to repost a pic that was originally shared by his 28-year-old girlfriend. Despite many public sightings together, the post marks the first time Chris has mentioned Katherine on Instagram.
Unfortunately, the photo and lengthy message were of a devastating nature, calling attention to one of the victims of the Woolsey fire. The aforementioned victim is William Thach, a children's book author who served as a high school tutor for all four of Arnold Schwarzenegger and Maria Shriver's children.
In addition to losing his home -- which, Katherine said William has "passionately been working on... for the past 10 years" -- the author also lost 3,000 copies of his velvet covered children's book, The Girl Who Saved Christmas.
"The beautiful home he built by hand for so long, for himself and his dog, Welly, including all of his possessions and memories of passed family members that were kept inside that house, are all gone," Katherine wrote.
Seeing the message, Chris immediately reposted it on his Instagram.
The couple's recent social media activity comes just days after they were spotted having breakfast with Katherine's father, Arnold, and his girlfriend, Heather Milligan, in Santa Monica, California.
A source recently told ET that Chris -- who announced his split from wife Anna Faris in Aug. 2017 after nine years together -- and Katherine have been inseparable since falling for each other, adding that she has the “full support” of her parents.
"The moment Chris and Katherine started dating, everything fell into place and they seemed inseparable," the source said of the couple, who were first photographed together in June. "They just love each other's company and have so much in common."
"They spend a great deal of time together,” the source added. “Chris and Katherine have the full support of her family and Maria [Shriver] feels they are a match made in heaven."
Meanwhile Chris and 41-year-old Anna -- who is currently dating cinematographer Michael Barrett -- recently finalized their divorce, agreeing to live within five miles of each other for the next five years, until their 6-year-old son, Jack, completes sixth grade.
“Anna and Chris have always maintained a respectful relationship after breaking up," a source told ET. "From the beginning, their main focus has been their son, Jack. Anna and Chris support each other in their new relationships and want one another to be happy."
The former couple even celebrated Halloween together, along with their son and new partners. See below for more on how they spent the holiday: