The Kardashians are honoring their late father.

Today would have been Robert Kardashian's 72nd birthday, and his children have been sharing sweet messages of the late lawyer on Instagram and Twitter. Kim Kardashian West shared a photo of her dad, writing, "Happy Birthday dad! So much has gone on in our lives since you've been gone, and I know you have been my guardian angel seeing it all unfold! I love you and miss you so much!"

PHOTO: Kim Kardashian Shares First Official Image of Son Saint West

The 35-year-old reality star also shared the first photo of her son, Saint West, on her website and app, explaining, "Today is my dad's birthday. I know there's nothing more in the world he would have wanted than to meet his grandchildren. So I wanted to share this pic of Saint with you all."

Kourtney Kardashian also had kind words for her late father, writing, "Happy birthday to my favorite man in the world who taught me everything. I know you are with me but I wish I could hug you. I love you Daddy."

WATCH: Kanye West Pays Tribute to His Late Mother and Robert Kardashian Sr. With Airbrushed T-Shirt

And Khloe Kardashian echoed her sister's sentiments, sharing, "To the best man I've ever known, happy birthday daddy. I miss you! I miss you! I miss you! Man... I wish we had more pictures together."

Robert Kardashian died in 2003. He famously was on O.J. Simpson's defense team during the former football star's double-murder trial, which is being detailed in FX's American Crime Story: The People v. OJ Simpson this season, with David Schwimmer portraying Kardashian.

WATCH: EXCLUSIVE: Kris Jenner Gives a Saint West Update

Meanwhile, Kanye West took the time to honor Robert, as well as his late mother, Donda, on a piece of clothing after his Yeezy Season 3 album listening event.

Watch the video below.