Thank you for your patience in waiting for the reply to your excellent question. I have been away on vacation and have only just now returned.
This challenge is quite common among children of this age. In varying degrees I think that each mom at some time or another has had to deal with this challenge. Remember that children are adults in the making and that the challenges such as this are gateways to learning.
In our family we have often said that 'arguing and backtalking' are roadblocks to accomplishing the tasks at hand so that we are able to get on with the fun activities that we hope to enjoy as a family. The day will be running along smoothly with a hum of productivity and then from nowhere someone decides that it is time to slow the works down with comments that are disrespectful. Such comments call for attention. It is neither holy or helpful for children to behave in the way that you describe.
In our house we have tried many ways to discipline ourselves (I can be very negative at times as well) from the useless behavior of negativity. Sometimes comments need to be ignored and dismissed (silly prattle that often happens between siblings who love each other), sometimes they need to be addressed immediately (outright disrespect towards parents or older siblings in a position of authority) and then there are certainly those times when the comments are misunderstood and need to be explained (sometimes what seems like a negative comment may be be a comment that has merit and needs to be addressed).
I admire you very much and sense that you are working and striving to raise holy helpful children who will be a comfort to you and your husband as well as to one another. Keep impressing upon the children that they are a team and as such it is important that each member of the team do their part to help the family get to the end of the day in a holy way. One of the best ways to help all the children remember that their siblings deserve respect is to have them pray for one another at the end of the day. Praying the rosary out loud and offering up the mysteries for the intentions of one another is a powerful witness to the deep love that they have for one another. Siblings do not often realize how important their witness is to little ones but they feel this more when they are praying for each other.
Keep working at this important challenge. It is indeed worth your efforts and your time. Remember that children come to us ready to learn and that they are learning each and everyday. If a challenge presents itself then it is time to work on that challenge. Jesus wants you to deal with the challenges and He will empower you to speak accordingly and act in a holy way to overcome the challenge.
Let us pray this evening for those families where the siblings are estranged from one another. Lord we ask that they allow old arguments and grudges to melt away and to seek reconciliation with one another. Lord the gift of family is a treasure beyond whose measure we may never appreciate until we are reunited with our entire family in Heaven. Help us to understand the treasure of family. Amen.
Sending out a prayer,