I think they should have the resonance to their time with Magneto - both as pawns in the Brotherhood, and then the years they believed they were his issue. But I also think they should have the resonance and relationship to the Roma they also thought were their family (or are, sorta).
I think my take on High Evolutionary is that he created "artificial" mutants with the twins. He did something to their genes and dna that make them mutants, but not through the normal evolutionary process.
In that sense, he has gone beyond even mutants' evolution as a "next step" in mankind. Wanda and Pietro are that and now they should integrate that into their lives and essence.