Rob Kardashian Makes Rare Appearance at Sister Khloé's 40th Birthday Bash

Rob Kardashian rang in sister Khloé 's 40th birthday with the whole family!

In an Instagram video showing off the reality star's festivities , the 37-year-old was spotted sitting near Khloé as a purple cake was brought to the table.

That same day, Rob also took to his own Instagram Stories to wish the Good American co-founder an amazing day.

"Happy birthday to my A1! I love you so much!" he captioned a sweet throwback photo of him and Khloé as kids .

Kim Kardashian also joined in on the well-wishes.

"Welcome to the f------ 40 club baby!!!!!" she wrote next to a snapshot of the two sister together. "I feel like you have been waiting for years to finally be done with your 30’s and the time has now come."

"I know this will be the best decade of your life filled with so much love and happiness! I’m so excited for you to experience this because I know how good it is, and no one deserves this more than you!" she gushed. "What a crazy life we live! I couldn’t do it without you by my side! Thanks for being the best friend and sister a girl could ever dream of."

Her ex and father of her children — daughter True , 5, and son Tatum , 1.5 — Tristan Thompson also wrote a heartfelt tribute to the mother-of-two .

"Happy birthday, Khloe," the basketball player penned via his Instagram Story. "You are the best mom. You are my best friend . And the most incredible human being I've ever met."

This comes one year after Khloé admitted she was looking forward to saying goodbye to her 30s and heading into a brand new decade after years of ups and downs in her personal life.

"Most people are scared to turn 40. I have hated — every day of my 30s has been agony . Like, what the f---!" she said at the time.

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"Of course, I've had some incredible moments in my 30s. I mean, I have two beautiful kids, I have great, great moments, I’m not — this has nothing to do with that," she clarified. "Besides that though, every other day has been f------ torture . I’m actually p------ I’m only turning 39 this year."