Kim Kardashian and Kanye West renewed their wedding vows following the birth of their fourth child, son Psalm. Kardashian, 39, and West, 42, showed their vow renewal ceremony during Sunday's episode of "Keeping Up with the Kardashians." Kardashian and West married in May 2014 and are parents to North, 6, Saint, 3, Chicago, 21 months, and Psalm, 5 months. "I just want to plan something special and take charge of this," Kardashian said in a confessional shot. "So, I thought let's just do something fun and sweet in our backyard and just make more of a memory." Kardashian initially wanted to surprise West but learned the rapper was also planning a celebration for their anniversary. The pair agreed to an intimate ceremony with family and friends. "I think it's so special that all four of our kids are here," Kardashian said. "I tried to get all of our wedding party out. It'll just be really sweet and I'm excited everyone is coming over." Kardashian and West did not film the ceremony, but did show Kardashian practicing her vows, which she wrote for the occasion. "You are my husband. You are my best friend. My biggest believer and my one true love," she said. Kardashian's sister Khloe Kardashian voiced her love for Kardashian and West in tweets Sunday evening. "Long live KIMYE," she wrote. "I loved celebrating this day. KIMYE day." Kardashian celebrated her 39th birthday on Monday. She spent Sunday with friends and gifted them with products from her Skims shapewear line ahead of the occasion.