The tragic complexities in the relationship between 2 siblings with a big age gap.
I get Ivan’s pov (I’m the youngest child), the way he views Peter’s actions toward him and how he interprets them. What’s new to me is Peter’s pov. So seems like to me after reading intermizzo and observing ppl around me that the oldest child is under big responsibility assigned to them by parents or younger siblings or even themselves, the way they start taking responsibility in protecting their younger siblings and their parents (this is not theoretically speaking, this is real, observed in a real life events), therefore small details like how to speak to your younger sibling and how to respect them or at least treat them like how would you treat any other adult, when it come to this they won’t calculate the impact of their words and actions, on the other, the younger sibling who is a sucker to details would start thinking, becoming more and more introspective, or blaming the older sibling, thinking that they don’t like them (yes older siblings love their younger siblings, but how many of them like their younger siblings?), the younger sibling starts psychoanalyzing the older, becoming more judgmental, and thus when the clashing starts, the older who’s already judgmental and the younger realizing that they’re not the wrong party and finally trying to stand up for themselves.
In the book things got really ugly and they made up really nicely. Sadly, in my little observation, younger and older will never make up, there’ll be always ugly times, followed by cold silence, then friendly presence. And how would they ever have a relationship with more than that? the very big year gap, different generations, different responsibilities, different mindsets, parents becoming different with the years and they raise their kids differently. The saddest misunderstanding! and whose fault is that?

Edit: elder*/ eldest* I guess