Not only that they are supposed to be twins.
If Grace Fulton (21) is indeed Mary Marvel, Billy's twin sister,
Not sure if she is playing an adult ("transformed") Mary, a kid (non powered) Mary or somehow both? , as she neither matches Zach Levi (37), or Asher Angel (15)
Still they all look pretty great for the parts.
As does Dwayne Johnson for Teth Adam
And i'll be more than happy with either Mark Strong or J.E. Haley for Sivana