I don't care for Kolton/Colton, and I also think it's too similar in sound to Kanyon. And I don't care for themes, and if both of your twins have K names, you'll have 3 K's--KKK! Please, no.
Other suggestions:
NolanBrennanHaydenDaltonQuinnTannerWestonRileyRyder
SawyerPaxtonAsherMasonGageLucasRaleigh