Credit: Instagram

Today would have been Robert Kardashian's 70th birthday, and so his four children  Kim KardashianKourtney KardashianKhloe Kardashian, and Rob Kardashian  are sharing throwback photos on Instagram to honor his memory.

Robert  who passed away from cancer in September 2003  was born on February 22, 1944, meaning he would now be 70 had he still been alive today. Proving that he is not forgotten, his four kids posted very sweet messages along with throwback pics of themselves as kids with Robert.

"Happy Birthday dad!" Kim captions her photo (at right). "Can't believe you would have been 70 today! Bet you're up there eating tons of Ralph's cake! Miss you & love you!"

Khloe posts a cute one of her much-younger self having recently gotten face-painted, with her dad next to her, holding a football. "Happy birthday daddy!" Khloe captions it. "Forever missed. Forever loved! Forever my guardian angel!" 

Kourtney writes, "Happy Birthday Daddy! We would have had a big party tonight! I wish I could touch your face."

And Rob captions a pic of himself as a kid with his face pressed close to his dad's, "Missing You  will be forever but forever Thankful. Happy Bday Dad, Love You and Miss You every day!"

This is extremely touching, and we wish the Kardashian family all the best on this emotional day.

Sources: Kim on Instagram, Khloe on Instagram, Kourtney on Instagram, Rob on Instagram