Im no expert , but how can dash and have super speed, and how can violet have invisibility and the ability to make force fields if their parents powers were super strenght and super flexibility? Shouldnt they have inheritated their parents powers?
I think the powers are chosen by a set of Genetics. Therefore, any superpower is possible from any super-parents. Did that make sense?
The reason is because it would be so lame if all 5 members of the family had the same 2 powers.
And you have to remember, these guys are supers. The way genes are passed down in humans doesn’t have to be the same way for superhumans. Maybe powers just don’t work like that.
I think you get your powers based on ones personalities.
Because then their superpowers wouldn’t fit their personalities. Didn’t you know evolution is heavily based on poetic license. Why else would the Dodo have become a stupid bird? It did so in order to fit it to the name Dodo.
You know, I was wondering the same thing. 
Maybe speed and invisibility were recessive traits that were passed to Bob or Helen, but the genes for their abilities masked them, but were passed down to Dash and Violet where it was then expressed in them.
Sorry if that doesn’t make sense, my Biology memory is a little fuzzy.
It does seem a bit odd, though there could be certain explanations I suppose.
But sometimes applying genetics to such things can make things go horribly wrong. I’ve seen creators try to do this and mess it up. Or infer unfortunate implications accidentally.
This has little to do with genetics- but my own random thoughts on their powers. Dash is hyperactive and so has speedy powers, Violet is a teenager who feels out of place so her powers can keep people away and hide her from sight. Many a teenager has the ‘want to be invisible’ moments. Or alternatively ‘I feel invisible’ moments. Or would like a forcefield to keep people out.
I’ve not got my science hat on but here’s some random patterns with the powers:
I think the thing is that while I guess since Dash’s powers are in the PHYSICAL area. Dash’s powers like his fathers are like an extremely increased/multiplied version of what NORMAL people can do (run fast versus good strength). Most of us can run too. We can also lift/push things. We just can’t do it at the level they can.
Helen’s powers could… almost be argued to be in this area I guess. We can stretch a little, but obviously not like her! We can’t extend our body area like… actually now that I think of it her ways of stretching are too different to the regular definition really, so her powers are on the fence I guess… still physical though.
Violet’s powers however are pretty out there given the rest of her families. We can’t turn invisible or throw forcefields. At all. Her powers are pretty different.
Jack-Jack’s is even more bothersome though really. He seems to be able to affect his own matter- change himself into things, make himself faze through walls. He’s a morpher, possibly able to arrange and even change is own atoms.
He can change into anything though he remains his equivilant size it seems.
(That’s Jack-Jack’s MAIN power to me plus the eye beam thing.)
But maybe that could almost be considered in his mother’s area. His mother’s breaks the laws of physics! She can also… affect her own body in a weird way? Like Violet’s invisibility?
I don’t know… maybe Dash’s powers almost fit given his parents powers even if they’re not really the same. Maybe… maybe Jack-Jack’s is… almost in his mother’s area. But Violet’s forcefields and Jack-Jack’s eyebeam thing is pretty different.
I don’t think they should have the same powers. Besides, this is the hair thing all over again. Recessive trait from the grandparents. Or, like someone said, it depends on their personality, especially since that’s how they decided what character got what power, anyway. I like that idea.
I think it could be that Helen or Bob carry the gene that grants their offspring super powers. Now I think that gene can be altered or modified so that the offspring could have differnt powers, but if one were to possess the SUper Hero gene, then he/she should have powers.
Or, the other way around could happen too.
I always just assumed there was a ‘super’ gene that gave you the ability to have a power, but your personality / upbringing determined which power you would settle with. Sort of like the mutant gene in X-Men.
I assume that that’s not how superhero genetics work.
I agree with you. It’s just a general gene, like having freckles, and the result could be anything.
I was thinking the same, though like people have said, it’s probably just the superhero gene.
I suppose super powers being genetic makes sense, but then wouldnt Bob & Helen assume that Jack Jack does have powers of some kind? I mean, they go through the movie thinking that he doesnt. So how would that work? Do they think he has a genetic defect of some kind?
I would think that there is just a super gene, but that is a good question you raise Lennonluvr9. Maybe they were just hoping he didn’t. 
Maybe…But i find it more unique that each character can do something different. 