The Force Awakens
There are plenty of examples of the attraction between Rey and Kylo Ren in The Force Awakens.
Let’s take their first encounter: Kylo Ren deflects Rey’s shots, before freezing her altogether. He then uses the Force to read her mind and she passes out. Instead of having some of his Stormtrooper minions pick her up or drag her to his ship, he scoops her up himself. Not only does he scoop her up, but he also carries her in a similar way a husband carries his new wife through the threshold of their first home.
This is more of a foreshadow then an actual example, but it is quite telling about Ren’s initial and maybe even unrealized feelings for the beautiful scavenger.
Later in the film, Kylo Ren interrogates Rey to find out the location of the island Luke Skywalker is living on. Rey makes a comment about a creature in a mask, and Kylo is more than happy to remove it for her. There is a brief hesitation on Rey’s part when she sees his face like perhaps she finds it to be an attractive one.
The final example of mutual affection between these two in The Force Awakens is in their final duel. When they are fighting, instead of saying how he is going to kill her, Kylo Ren tells Rey she needs a teacher.
In his heart, he realizes he would rather have her on his side, then for her to be dead, and while that is odd soil for the seeds of love to be planted, they clearly were.