to mix with, to associate with, to join, double X radical (no. 89)
爻 centers on the idea of crossing or intertwining: mixing, associating, or joining things together. The radical sense is the same crossed shape used as a component in other characters.
爻 is a pictograph of crossed lines, representing intertwining or mixing. The doubled X shape reinforces the idea of interaction or joining.
See the two crossed X shapes stacked on top of each other, like two things intertwining and mixing together. 爻 is about joining and associating.
For コウ, imagine two crossed sticks forming a simple coat rack: coat -> コウ, and the crossed shape mixes the sticks together.