Make an “Equal widths” constraints between your view and the super view with multiplier 2:3 for one view and 1:3 for the other. See picture. “Equal height” if you want to split in the other direction.
Make an “Equal widths” constraints between your view and the super view with multiplier 2:3 for one view and 1:3 for the other. See picture. “Equal height” if you want to split in the other direction.