S.H.
I have 2 kids, boy and girl, 4 years apart.
Daughter is 10, son is 6.
I do not expect my eldest (my daughter) to be the default "example" for her younger sibling. That is a big load on a child's shoulders and it can be stressful and resented. If you make the eldest child the example.
Anyway, with my kids, I always EXPLAIN, the developmental differences, between them per their ages and development. They are just different that way. Not, the same. Hence, their behavior, reflects their age/development. So, they cannot expect each other to be/do/act, the same nor understand things the same.
And I don't side with any of them particularly.
But all siblings, will have times they have conflicts.
Normal.
BUT you teach them about BEING a team, about being family, about having each other's back, etc. SO that, they see each other as COMRADES and not as, adversaries.
That is what I do with my kids.
The eldest child, should NOT be the one that has to be all PERFECT and an example. It is not fair. At all.