A source told PEOPLE this week that while Chyna is "giving pushback," Kardashian wants dual custody of their 4-month-old daughter Dream

They may not be on the best of terms these days, but Blac Chyna didn’t forget about her ex-fiancé Rob Kardashian‘s birthday.

The reality star took to Instagram on Friday, Kardashian’s 30th birthday, to send a simple shout-out.

“Happy birthday @robkardashian,” she captioned a smiling photo of the two from happier times.

PEOPLE confirmed in February that Kardashian and Chyna, 28, had called it quits after a year of volatile ups and downs, during which they welcomed daughter Dream Renée in November.

On Wednesday, a source told PEOPLE that Kardashian’s focus is on his 4-month-old baby girl — and while Chyna is “giving pushback,” he wants dual custody of their child.

“They are still figuring things out but [Chyna] will certainly do whatever it takes to have Dream be with her for the majority of the time,” said the insider, adding that Kardashian’s mother Kris Jenner is “backing Rob up 100 percent and won’t let Chyna get away with anything that’s less than fair.”

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And Jenner isn’t Rob’s only source of support: His sisters are standing behind him as he learns to navigate his new life as a single dad. The whole family also took to their apps and social media on Friday to share sweet birthday messages.

“The entire Kardashian family is there for Rob as well and supports him wholeheartedly,” said the source. “They are prepared to protect him in whatever way they need to.”