Yeah his sister and Clea are not flame people, Furnance Face simply morphed himself to look that way. You know, magic.
Also yeah Raven was raised by her moms folk of magic users in DC.
In Marvel not sure as in comics there are no big communities for magic folk ( just in Asia, but more exclusive) and the dimensions.
Dormammu should have a foot hold on her as a result not just lack of community, but I see him as very direct in fatherhood.