So then let us pursue what makes for peace and for mutual upbuilding.(Romans 14:19 ESV)
Unless you only have one, very young, child then peace is unlikely to be the foremost thought on you mind when they are awake.
Sibling rivalry is just one of those behaviours we have to endure in our kids, but it is not something we want to encourage.
There are dozens of books written on how to control and improve children’s behaviour, how to be a better parent &etc. However, while we should use what means we can to teach good behaviour to our children, we cannot give them a heart of peace. God can.
It is good and right and necessary to ask God to give our kids hearts to pursue peace.