Brandon left a sweet comment on one of Kendall’s Instagram posts that featured Kylie on Tuesday.
“A couple of cute kids right there,” he wrote, even adding a few emoji hearts to the comment.
In the shot, Kendall, 22, and Kylie, 20, looked natural and grinned widely.
“Alien sister,” Kendall wrote in the caption of her Instagram gallery, which shows the sisters first smiling from a distance and then huddling up for sultry selfies. At one point, Kendall placed her chin on Kylie’s shoulder as she rolled her eyes back.
Brandon and Brody share father Caitlyn Jenner with Kendall and Kylie.
In May, Brody revealed that Kendall and Kylie chose not to attend his June wedding to wife Kaitlynn Carter.
“My two little sisters, we never even heard from them. They never even RSVP’d I don’t think,” Brody, 34, told PEOPLE
“We sent them an invite but we just never heard anything back,” he said. “Well, they’ll be missed. I would have loved to have had them there.”
RELATED VIDEO: Brody Jenner Says Sisters Kylie & Kendall Jenner Never RSVP’d to His Wedding: ‘They’ll be Missed’
Meanwhile, Brandon served as Brody’s best man.
In February, Brody also revealed it’s been “a couple years” since he last spent time with Kylie, who gave birth to her first child, daughter Stormi, that same month.
A source previously told PEOPLE that Brody was “never close” with his step-siblings, Kourtney, Kim, Khloé and Rob Kardashian after Caitlyn married Kris Jenner.
“He didn’t spend a lot of time with his dad when his dad married Kris, so he didn’t see them as much,” the source said.
And while Brody spent time with Kendall and Kylie when they were younger, they’ve grown apart over the years.
“As much as they love them, they’re not close,” the source added. “It’s unfortunate.”