Idk how to get him to like me.?

so i meet this guy lets call him Chester and his twin sister lets call her Mia in 6th grade. i have always like Chester more then a friends but not major crush just the like like if he asked me out i would. so my old best friend and current enemy nay nay always helped me go out on a double date with him. so if i tried to hang out with just me and Chester alone Mia would get mad. so i have to invite her everytime. i want to know how to get Chester to like me too. any suggestions?? Thanks for the Help