She wrote, "I’m sitting here struggling to write a caption because there are sooo many things i want to say. This boy changed my life... he made me “MOM”. I could not be more proud of this kid! So smart, funny, sarcastic and bright... and he is 8. EIGHT YEARS OLD. Happy birthday to my first born! #IsaacElliott @theisaacerivera & thank you @wendydarlingphotography for capturing this photo! 📸"
The birthday boy is also the oldest of Kailyn's children and has two little brothers, Lincoln and Lux.
It's pretty clear he's the best big brother, ever.
Ready for school!
Lincoln adores his big bro!
And Isaac adores his brothers as well.
Looks just like mom.
He learned how to snorkel.
Watching mom graduate.
The dogs clearly love him too!
As seen on the show, he takes his school work seriously!
The two clearly love their tacos! Too cute.
Such an adorable moment with former stepdad, Javi Marroquin.