"A lot has changed, but ... the most important stuff didn't," Jenner's eldest son wrote on Instagram
Burt, 37, took to Instagram on Thursday to post a fiery defense of Caitlyn and her transition.
“So obviously a lot has changed But thankfully for me, the most important stuff didn’t,” Burt wrote as the caption to a photo Caitlyn, 65, standing and raising her fist triumphantly in the air behind two young girls driving a pink toy car. “My dad still loves toys, fun toys, still likes to go fast, still loves adrenaline And will still whip your ass at ANYTHING Yup all you haters, my dad will still probably whip your ass at 65 with implants.”
Burt continued his defense of the former Olympian: “Oh ‘no’? There were a lot of world class athletes that said the same thing And lost Sure, I believe you, since you have comparatively accomplished so much with your life.”
Burt is Caitlyn’s son with her first ex-wife Chrystie Scott. The two were married from 1972 to 1981.
Caitlyn and Scott are also parents to Burt’s sister Cassandra Marino, 35, who told PEOPLE in June that her “relationship with Caitlyn is much better than with Bruce.”
“She is trying harder and there is a softness to Caitlyn that is new to me,” Marino added. “I think part of that is that when someone is happier, they are just nicer.”
Burt and Cassandra found out that Caitlyn (then known as Bruce) was transgender when they were 13 and 11 years old, respectively. According to Caitlyn’s Vanity Fair cover story, in which she made her public debut as Caitlyn, their mother told them about their father’s “identity as a woman.”
RELATED: How Caitlyn Jenner’s Relationship with Her Children Has Changed
[BRIGHTCOVE “20927896” “” “peoplenow” “no” ]
“I have high hopes that Caitlyn is a better person than Bruce,” Burt said in the VF article. “I’m very much looking forward to that.”