We went off to Canada for three weeks, adult holiday, leaving our then 18 and 21 year old in the house together, with a certain amount of trepidation as to what we'd come back to. Although their older sister, my step daughter did call in on them from time to time.
Younger son, conversely the most responsible or so I thought, rang us up complaining about older brother being over zealous laying the law down and being totally unreasonable. We were very sympathetic until we got home and our older one told us that his brother had had several friends home one evening, "one had too much to drink, didn't make it to the bathroom and was sick in your bedroom, and I was the one who cleaned it up"
what was he doing in our bedroom God only knows Well apart from a falling out between them, and the house being filthy, we made them spend the weekend cleaning it, all was well, they coped.