"He's sad," a source close to Humphries tells E! News. "He doesn't want a war. He's laying low."
Instead, the basketballer has been spending extra time in the gym back in his home state of Minnesota and leaning on family and friends for support since Kim filed for divorce.
"He's just training and working out again, getting ready for basketball season," the source tells E!. "He's taking it day by day and surrounding himself with family and friends in Minnesota."
In the meantime, the Kardashian family did some celebrating of their own last night for Kendall Jenner's 16th birthday sans Kim and Khloé, who were en route home from Australia.
The tight-knit family celebrated by having dinner together, and Rob said time has flown by. "I can't believe my sister's 16," he told E! News. "She's such a great person. I never want her to change."
Birthday girl Kendall even shared a pic of her cake via Twitter, posting "Happy birthday to ME!"
Rob also gave his thought on Kim's personal turmoil, saying: "She's obviously going through a lot right now, but we're always together as family and I feel like that's the most important thing."