updated 08/18/2013 AT 5:00 PM ET
•originally published 08/18/2013 AT 6:20 PM ET
The reality starlet and Kanye West went to Oklahoma with 2-month-old daughter North on Saturday for the funeral for the rapper’s grandfather, Portwood Williams Sr., who died on Aug. 10 at 98 years old.
“That’s why they weren’t at [sister] Kylie’s birthday,” a source confirms to PEOPLE. “They brought North, too. Her first trip.”
Back in February, Williams voiced his approval for his grandson’s girlfriend, calling Kardashian “beautiful.”
“And she’s just as sweet as she is beautiful,” he told New York’s Daily News. “That’s what I liked about her!”
Because they weren’t able to celebrate Jenner’s Sweet 16th party on Saturday, the couple – who welcomed their new addition on June 15 – sent some very special guests in their replacement: hip-hop artists Drake and Big Sean.
Reporting by JENNIFER GARCIA