Collin Gosselin is showing "gratitude" for some important people in his life, but that doesn't include his mother, Kate Gosselin.

The son of the former "Jon & Kate Plus 8" star took to Instagram late Wednesday night to share a belated high school graduation post. "Better late than never!" Collin began his caption.

"I wasn’t totally sold on the idea of making a graduation post, as most students graduate, therefore making it not such a big deal. So I decided to anchor this post more towards gratitude for mentors, friends, and of course family," he continued.

Collin gave a special shout-out to his sister, Hannah Gosselin, for "standing by me and supporting me," as well as his father, Jon, and his ex-girlfriend, Colleen. Jon and Colleen separated in 2021 after seven years of dating, Entertainment Tonight reported.

JON GOSSELIN SAYS HE ‘HAD 8 GRADUATIONS THIS YEAR' BUT ‘ONLY ATTENDED 1’ AMID ESTRANGEMENT FROM 6 OF HIS KIDS

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"I would like to thank my dad, who has taught me so much about running into hard times and moving past them, about resilience. Thank you dad for always supporting my decisions, and having my back when I bite off more than I can chew," Collin wrote.

He continued, "When you think of someone you want by your side, you think of Colleen. And as I’ve told her many times, she is my motivator for being successful in this world."

Kate Gosselin and her eight kids

Collin Gosselin, one of Kate and Jon's sextuplets, left his mother out of his graduation post. (Donna Svennevik/Disney General Entertainment Content via Getty Images)

Collin wrapped up his lengthy caption praising his Army Junior ROTC instructors. "No hate towards the Army, but the challenge of the Marine Corps just appealed to me more. Just thought I’d clarify that," he added with a laughing face emoji.

He gave his followers an update on his college plans, writing, "I will be studying Mechanical and Industrial Engineering in college! Can’t wait."

Notably missing from his post was Collin's mother, Kate. Jon told People magazine that Kate did attend Collin and Hannah's graduation, but the former couple did not speak.

Collin Gosselin, Jon and Kate Gosselin

Collin Gosselin, son of Jon and Kate Gosselin, thanked his father for "always supporting" his decisions. (Jon Gosselin Instagram/Getty Images)

"Hannah invited Kate and… we saw each other, but there was a whole football field between us," Jon told the outlet. "I talked to Hannah and Collin before graduation to make sure that it was gonna be cordial."

Collin told Entertainment Tonight in November that his relationship with his mom was severed after he was sent to the Fairmont Behavioral Health Institute.

"After being there, I didn't have a relationship with her," Collin told the outlet at the time. "Even before [being] there, I don't think we had much of a relationship and I think that just kept tearing it even more down."

Jon, Hannah Gosselin

Collin gave a special shout-out to his sister, Hannah Gosselin, and his father, Jon Gosselin. (Robin Roslund)

Collin told the outlet that the pressure of his family being on a reality television show led to the estrangement with Kate.

"I want to believe it was because of TV and what being in the public eye does to a family. I think it tore us apart," he shared. "It gave us less time to actually be together as a family, [and] more time to be in the public eye."

Jon shares twin daughters Mady and Cara, 22, and 19-year-old sextuplets Hannah, Collin, Aaden, Leah, Joel and Alexis with his ex-wife.

Jon Gosselin and ex-girlfriend, Colleen

Collin also thanked Jon's ex-girlfriend, Colleen, in his Instagram post. (Greg Doherty/Getty Images for Brooke Lewis and Mark Bellas)

Jon previously told People magazine that he had eight graduations this year, but only attended one because he only has a relationship with Hannah and Collin.

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"I had eight graduations this year," Jon said. "I only attended one. The only kids I see and talk to are Hannah and Collin. So I've been pretty much estranged from Mady and Cara for nine years."

Jon, Kate Gosselin

Kate Gosselin and Jon Gosselin divorced in 2009 after 10 years of marriage. (Brad Barket)

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Mady and Cara graduated from separate colleges in New York this year, while the sextuplets graduated from high school. 

In 2009, Jon and Kate divorced after 10 years of marriage following cheating allegations. From 2007 to 2017, the family starred in the TLC reality series "Jon & Kate Plus 8," which was renamed "Kate Plus 8" after their divorce.