I like to think that Luke and Leia both had visions as young kids.

Leia saw her real mother, but they were images of her, and feelings of love.

Luke yearned to see his father and know as much about him as possible. He reached out with his force abilities to seek answers (in his dreams), and Yoda was the only one listening. I think this is why Luke feels like he’s been to Dagobah, because when Yoda was calming Luke down with the force, he could actually see Yoda and his surroundings, just like a dream.

Maybe I’m wrong and this is explained in the Kenobi series, we’ll just have to wait and see.

Edit:
Luke has no memory of his real mother, and Leia has no memory of her father.

This could be something Kenobi or Yoda did to ease their pain, or hide it from Vader, the Emperor or the inquisitors.