Board Thread:Off Topic/@comment-25396609-20190908002326/@comment-26397825-20191003031724

The closest I've come to a shared semblance is where I gave a pair of twins two sides of the same coin. One creates golems out of shadow, the more shadows he takes the stronger the golem is. The other uses her own shadow to manipulate the world around her, the darker her shadow the more powerful it is. Technically they're both shadow manipulation semblances, but they are very different in function and abilities.

You could do something similar here; have the base idea be the same but approach it from two different directions. It's just like a set of twins; the dna may be the same (even the egg may be the same if they're identical) but their personalities and thought processes will be different.