How often is it normal to fight with others in your household?

It's not normal at all here. Maybe once or twice a year at most.

I had some arguments with the brother when we was younger love, that was nearly 20 years ago.

Really shocked me to have arguments with the ex when we moved in together. We alway got along so will, and we never argued before living together, but he argues with everyone so the problem is him, not me 🤪