The father of one looked happy and healthy as he posed for pics with Khloe and Kourtney Kardashian, as well as Kendall and Kylie Jenner. Rob, wearing a black sweatshirt, black pants and sneakers, smiled wide as he reunited with his family and friends, like Scott Disick and Tristan Thompson.
"Baby welcome to the party," read the caption on one image. Another was captioned, "Woo back baby."
Rob has been noticeably absent from the spotlight in recent years and has rarely shared photos of himself on his Instagram.
A source told ET in March that the former reality star was "doing really well." "Rob continues to work on staying healthy for himself and his daughter, Dream," the source said.
"He and his family have a great relationship, and truly value family time. He loves having his nieces and nephews around and having them spend time with Dream," ET's source added. "Now that most of the family has young kids growing up together, the family is tighter than ever."
"He goes to Kim's, he's worked out for, like, the past five days or so, and he's kicking a**, and I just want Rob to do what's best for him and what makes him happy," Khloe said. "And if that makes him happy, then we will all support him."
Kim told ET last November that she and her brother really connected "the past year or two."
"He's doing great," she said of Rob, before admitting, "He definitely is more low-key than all of us, and we love that and respect that."
The mom of four added, "We love having [Rob] around. ... He's doing really good."
See more on Rob in the video below.