Experience Tumblr Like Never Before
The relationship between Kai and Krux is good, yes.
Kai taking care of Nya without any help is also good, but
Kai goes to the museum after his parents dissappeared, and takes Nya with him. Afterall, he can't just leave her alone.
And so he searches for dr. Saunders for advise, he is an adult and would surely know what to do.
This could go two ways
Canon compliant
AU where everything is the same but hands of time takes a higher toll on Kai (possibly Nya too).
So 1. Either Krux ignores Kai or he gives him some pieces of advice and sends him on his way.
And 2. Krux gets guilt ridden because thei're just children. They can't do anything, they weren't even born then, they're not at fault. And so dr. Saunders becomes a constant in their childhood.
While tat all happens Nya just looks around and finds the samurai exhibit and nothing really happens.