Kylie Jenner's got some explaining to do ... according to her daughter at least. The beauty mogul dished to Kid Cudi about how Stormi is finally catching on to who her family really is.

On the first episode of "Big Bro With Kid Cudi," Kylie revealed now that her oldest kid -- 8-year-old Stormi -- is in school, she's started realizing her whole family is famous ... and she's demanding to know why!

Kylie -- who was surely preparing for this day -- says instead of just telling Stormi, she showed her. According to Kylie, they shared a sweet moment watching the pilot episode of "Keeping Up With the Kardashians" together.

They couldn't watch everything, because not all of it was age-appropriate -- Kim K discusses her claim to fame at the time, her infamous sex tape with Ray J -- so Kylie furiously fast-forwarded through those parts to give her daughter the gist of what put the family in the limelight.

Remember ... Kylie was only a year older than Stormi when the show first started! Crazy how time works.

Stormi is one of Kylie's 2 children with ex Travis Scott. Stormi's brother, Aire, was born in 2022.

Watch the video to find out why Stormi's innocent question ended up bringing Kylie to tears.