how do the deaths of romeo juliet and paris affect the way the capulets and the montagues feel about their feud

There is that whole "don't know what you have got until it’s gone" thing going on. When both families see the senseless loss of young life, they see the futility of their family spat.

Capulet to Montague- "oh give me thy hand...."

Montague pledges a golden statue of Juliet and the lesson is learned.