Advance their events. Each girl has her own story events, which need to be done before they are ready for the wedding events. The walkthrough has a step-by-step guide for the events of each main character.
I did it all as far as I know Vampire and Neya together, I also did Kay and Jaylin's beach scene, I also built Kay's farm, I just didn't do Sandra's quiz, they all have their scenes on, I guess only the post-marriage scenes are off and my relationship is over 200 with all of them
