Khloé Kardashian 'Didn't Really Get' Why Tristan Thompson Posted a Birthday Tribute to Her: Source

"Her family thinks he posted it because he wants to make himself look good," a source tells PEOPLE

Tristan Thompson‘s birthday tribute to Khloé Kardashian certainly raised eyebrows amongst her famous family.

A source tells PEOPLE Kardashian saw her ex’s Instagram post, but “didn’t really get why he posted it.”

“They have a child together, but are not together,” the source says. “Her family thinks he posted it because he wants to make himself look good. Tristan and Khloé co-parent True, but that’s it.”

As Kardashian turned 35 on Thursday, Thompson, 28, dedicated a rare Instagram post in her honor, sharing a photo of the star with their 14-month-old daughter True.

“Happy birthday @khloekardashian,” he wrote. “You are the most beautiful human I have ever met inside and out. Thank you for being an amazing mommy to our princess True. She is blessed to have someone like you to look up to. I wish you nothing but more success and sending you positive blessing your way. Enjoy your day Koko.”

The post came in the wake of Thompson’s latest cheating scandal, which is currently unfolding on the family’s show, Keeping Up with the Kardashians. The basketball player hooked up with Kardashian’s longtime family friend, 21-year-old Jordyn Woods, in February — less than a year after he first allegedly cheated just days before Kardashian gave birth to their daughter in April 2018.

On last Sunday’s episode, Kardashian claimed Thompson was full of remorse after the incident and even expressed suicidal thoughts. (Thompson has not publicly addressed the claim.) Regardless, the relationship is over for good. A source told PEOPLE this week that Kardashian has no intention of ever getting back together with the Cleveland Cavaliers player.

“She would never go back with Tristan,” said the source. “She knows that he will never change.”

Matt Winkelmeyer/Getty; Michael Loccisano/Getty

And Thompson was nowhere to be found at Kardashian’s birthday festivities on Thursday. The star “had a quiet birthday celebration” in the morning with her sisters and her daughter, a source told PEOPLE, and later threw a lavish but intimate bash at her house with friends and family.