"Psalm- you have brought such calmness and evenness into all of our lives," Kim Kardashian wrote in her loving birthday tribute
Kim Kardashian
Kim Kardashian
| Credit: Kim Kardashian/Instagram; Getty Images

Kim Kardashian has a lot to celebrate this Mother's Day!

The Keeping Up with the Kardashians star, 40, started off the day with a loving birthday tribute in honor of son Psalm, who turned 2 on Sunday.

"My Taurus ♉️ baby Psalm. He turns 2 today on Mother's Day. Such a special day to share together," she wrote on social media. "He's my child that looks most Armenian to me like my grandpa and reminds me so much of my dad."

"He is the sweetest baby ever!!! I can't even describe his smile and sweetness that everyone just feels when they are with him," she added. "Psalm- you have brought such calmness and evenness into all of our lives! All of your cousins and siblings love you so much! You really are the joy of our crew! Mommy loves you SOOOOOO much!!!"

Kardashian also shares daughters North, 7, and Chicago, 3, and son Saint, 5, with Kanye West, whom she filed for divorce from in February.

Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.

Kim Kardashian with her children
Kim Kardashian and her kids
| Credit: Kim Kardashian/Instagram

Kris Jenner also posted a loving tribute to the birthday boy.

"Happy Birthday to my youngest grandchild!!! My beautiful, precious Psalm who is the light of our lives!!! Thank you little Psalmy for bringing such magical joy into our lives with your amazing smile and laughter and your sweet personality!" she wrote. "Your tender spirit brightens every day!!! You bring such happiness to us ... and you just happen to be the best scooter 🛴 driver I have ever seen!!! Best in the land!!!!"

"Thank you for all of the love you give to me and what a blessing you are in all of our lives !!! Being your Grandmother is my greatest gift and I love you more than you will ever know!!!" she added.

Khloé Kardashian also shared several sneak peeks into Psalm's backyard birthday party on Saturday, including a sweet clip that showed him playing with a festive piñata.

Kim Kardashian
Credit: Khloe Kardashian/Instagram

A source recently told PEOPLE that Kardashian and West's divorce is proceeding smoothly, with the pair continuing to prioritize the well-being of their children.  

"Kim and Kanye are getting along," the source said last month. "They have both stayed true to their commitment to make the best situation for the kids."

"Kim is very happy that they have managed to keep things calm. She thinks Kanye is a good dad," added the insider. "She wants him to be able to spend as much time with the kids as he wants."

RELATED VIDEO: Andy Cohen Says 'Everything' Was Discussed at KUWTK Reunion — Including Kim Kardashian's Exes

Since filing for divorce, the reality star and her kids have continued to live in the Hidden Hills mansion she shared with West, 43. 

"They both agree that the less stress the kids experience, the better. Kanye loves his kids. He wants them to be happy," a source previously told PEOPLE. "He doesn't want to fight with Kim about anything."