system
Given the following post, respond as if you're commenting on Reddit:
human
[X-Men] Why are Scott summers and Jean Grey’s children always really powerful or special.

It just seems to me that the majority of their possible children end up being much stronger than the both them.
gpt
Jean Grey is a very powerful mutant, and Scott Summers is no slouch himself. 

As a rule of thumb children of two mutants have a merged power set of their parents with a spin of their own on top. Most examples are in Exiles, but in general it still works. Nocturne for one is daughter of Scarlet Witch and Nightcrawler, so she can teleport and shoot hex bolts, but also can possess people. 
Son of Magneto and Rogue had all powers of his father, but his touch transmuted living beings into steel. 
Ruby was a daughter of Scott and Emma Frost, so she could shoot eyebeams and transform into a ruby form.

So in hindsight it's no wonder that son of monstrously powerful psychic like Jean Grey would also end up a monstrously powerful psychic.