I have to agree we should be able to opt out of family members being rivals. I had my main sim’s father, who is King, ask him to be his Noble Advisor. When the job task to promise title came up, I had him promise the title to his son, which meant he had to join the Noble career. Now my sim is Prince and also his father’s Noble Advisor with the “Promise of the title”. He is currently a level 8 in the career and I refuse to promote him because I don’t want him to become his father’s rival.
I just wanted father and son to be Nobles and live in the same house indefinitely, with the promise of inheritance. If it’s promised why should they be rivals? Or atleast make the promise of title end the rivalry without ruining relationships.