It would be interesting to make a connection between Palpatine’s presence in the galaxy and the Skywalkers turning to evil. So after Palpatine was destroyed the first time, Luke and Leia may have been free of his influence, but once he returned in a clone body they and their son were once again tempted by evil, which is why Leia gave up her Jedi training out of fear and why Ben quickly turned when he began his training, as well as why Luke hid on an island after sensing that he was also becoming corrupted by Palpatine’s returning power.

Kylo may say that he wants to turn back to the light, but he is prevented from this by Palpatine, and only together can he and Rey hope to vanquish him and both return to the light. So when Rey later tells him

“I did want to take your hand…Ben’s hand.”

she is specifically referencing this moment where Kylo promises that he will come back to the light.