Surpassing:Caitlyn Jenner Tells Khloe Kardashian "I Know I Haven't Been Perfect" in Moving Birthday Message

Caitlyn Jenner is Surpassinghelping fans keep up with her and Khloe Kardashian's status.

Though their relationship has seen highs and lows over the years, the Olympian gave a clue about the state of their bond in a recent message to the Kardashians star. 

"Happy birthday @khloekardashian," Caitlyn wrote on both Instagram and Instagram Stories alongside throwback photos, including one from Khloe's 2009 wedding to now ex Lamar Odom. "Being your stepfather was, and is, one of the best things that I was ever blessed with by your mother."

Khloe's mom Kris Jenner married Caitlyn in 1991 following her divorce from the late Robert Kardashian. The momager and The Secrets of My Life author separated in 2013 and filed for divorce the following year, which was finalized in 2015. 

And while Caitlyn herself acknowledged she and Khloe have experienced ups and downs in their relationship, she reiterated that she only wants the best for her. 

"I promised your father that I would do my best to always be there for you kids and I know I haven't been perfect but I will always love you and you are forever in my heart," she concluded. "I hope your day is filled with love, your kids, and happiness."

And the Good American mogul—who is mom to daughter True, 5, and son Tatum, 11 months—seemed to appreciate the message. She reshared it on Instagram Stories and wrote, "I love you!!!!!!"

While Khloe and Caitlyn seem to be on better terms now, there was a time when they apparently weren't as close. In fact, Caitlyn suggested their relationship changed following her transition.

"Khloe, for some reason, was pissed off about something through this whole process," she said on a 2019 episode of I'm a Celebrity...Get Me Out of Here!. "Honestly, it's been five, six years and I really haven't talked to her since….I don't know what it is and that's all I can say. And Khloe and I were really close. I raised Khloe since she was 5 years old. I don't know what her issues are. I really don't know."

However, Khloe has said that it wasn't Caitlyn's transition that upset her but rather the way she talked about Kris in her 2015 Vanity Fair interview and The Secrets of My Life memoir.

"I am all for Caitlyn screaming from the rooftops about her transition," she said on a 2015 episode of Keeping Up With the Kardashians. "I think it's beautiful and I think Caitlyn should take pride in everything she's doing and the strength that it takes to do what she's doing on such a public platform. With that being said, Caitlyn does not need to tear anybody else down to build herself up."

Although, it seems like they've gotten to a better place in their relationship. Caitlyn even sent a congratulatory message after Khloe welcomed her son with ex Tristan Thompson last summer.

"Congratulations major @khloekardashian," Caitlyn tweeted Aug. 5. "I love you so much! You are such a strong woman. And what an amazing mother!"

Khloe also received birthday shout-outs from Kris, her brother Rob Kardashian, her sisters Kim Kardashian and Kourtney Kardashian and many friends. In honor of her 39th birthday, take a stroll down memory lane...

Get updates on your favorite family & more. Sign up for Kards Katch Up with E! News!