psycho gundam
The Nightmare of Solomon
also, sue storm + reed richards = franklin richards ------> rachel summers + f. richards = jonothan richards summers (hyperstorm)
it appears that the level of power of the child is somewhat dependent on the amount of radiation exposer of their parent(s).
for instance hank McCoy's father was a chemical engineer or something and he was exposed to radiation while at work, he then had a mutant child with low mutant power's.
on the other hand, reed and sue were both exposed to cosmic rays and were themselves mutated, they then gave birth to a mutant son with extremely high mutant potential.
mutant couples usually give birth to mutants that surpass the power of their parents (the only contrary case is graydon creed, but it is likely that his dormant X-gene will be passed on to his progeny).