No doubt it is not good.
Praying to Allah to guide them and give them taufeeq to give respect to others. No doubt it is very difficult to tolerate disgrace and insult. Now your question, yes breaking relation is qata e Rahem
According to Hadith actual sila e Rahem is when you are good with someone who is not good with you.
Benefit of sila e Rahem is Barakah in rizq and life and ease at the time of death and qabr.
You May make your visit less but do not stop.
And be in contact through calls and message by sending gifts
In’Sha’Allah I’m sure there behavior will change

For anger, there are few things:
– Be in the state of wudhu all the time
– When you feel angry drink water
– Change the topic, position and place
– Read surah Naas and Falaq and اعوذ باللہ من الشیطن الرجیم
لاحول و لا قوة الا با الله العلي العظيم