Siblings
Most people (especially grandparents) instinctively prioritize and want to entertain the younger sibling. They feel the older sibling should be more understanding but the older sibling is still a kid! This is why the older sibling tends to get jealous. Don’t neglect your older kid(s). I actually prioritize my older kid because the physical needs of the younger one inevitably shifts the balance the other way.
Many days I find myself trying to explain to Knox or Cy the job of a brother: Protect each other at all costs, is what I try to reinforce. Be an ally to him, even against us. Especially against us.