... well even if your Father talks to Ethan's parents... it does not mean, he will then become healthy or in the right weight zone.
BECAUSE.... Ethan's parents... have eating hang-ups TOO.
AND their house is their house and what they buy and feed their kids...are their 'habits' and how they eat too.
For a child, to become healthy... it takes the ENTIRE family... to ALL.... participate in that. So, Ethan's Dad and Mom... have to start to eat healthy and not buy junk, nor feed him junk.
What is happening as well... is they are emotion-eating.
Sure, you say your Sister is conscious about good nutrition... BUT... they are NOT eating that way. Being conscious of something, does NOT mean... the person then behaves healthily, nor for their children.
AND you said, that your Sister has her own eating issues.....
Ethan's parents... eat junk, buy junk, feed junk, and eat unhealthy AND... eat out of emotions/hang-ups about food.
SO... this... is the problem as well.
Then, Ethan's weight problems and eating habits... are only a symptom of ALL of the emotion-based/psychological eating.... 'habits' ... of his Parents.
So... if the ENTIRE family.... does not correct their habits and food constructs.... Ethan... will be this way. He is a child... he cannot correct it on his own... nor cook for himself, nor grocery shop himself for alternative healthy foods.... if his parents will not participate.... in that. Even if he is.... obese or overweight.
What does their Pediatrician say?
Your Father means well.... but tell him to stop the name-calling.... a child will be hurt by that, emotionally. And that is hard.... to then correct. It is the child's self-esteem, too.
I can understand how your Father feels 'desperate' about this.... he is worried about his grandson....
Ethan's parents ALSO... will probably be in 'DENIAL' about this and Ethan's weight. THEN, the only way to help Ethan and the entire family... is they ALL have to be on-board about it, AND seek Counseling... or at least a Nutritionist.... and they ALL need to exercise too.
It is a WHOLE change... in their lives and habits and emotional constructs about food.... MANY ISSUES... they ALL have.
It is not Ethan's fault... he is a child. It is his parents... that are ultimately harming him.
And gee, your BIL already has 2 HIGH-school daughters... that are Morbidly Obese. That is... due to the parent(s)....
all the best,
Susan