Here's the way I see it. I don't know how old Max is supposed to be but given how complicated and mature his noisy toys are, he's old enough to speak more than one word at a time and to follow Ruby's simple directions. The reason he is so ill-behaved is because he's being raised by his stupid bunny sister. Ruby is spread thin, between gardening and Bunny Scouts and band practice and school (I assume she goes to school but without parents around, who knows? She might spend some of days growing weed in the attic or playing violent video games or posting inappropriate pics of herself on the internet.)
OF COURSE Max doesn't listen to her. She's his sister, not his mom, and he knows that. OF COURSE Ruby is so particular and and impatient. Her little brother is a little brat and not only does she carry the burden of gardening and Bunny Scouts and band practice, she also has to cook for, bathe, discipline, educate and put her pesky little brother to bed. Those are not jobs for a sister, unless you're a Duggar. She should be allowed to be a child.
And why hasn't their grandmother called CPS yet??? Or taken them into her home- seriously?