We had exactly what you described happen aboard one cruise. A 14 year old was saving a whole row of seats in the theatre for the "big production show", while his father and mother enjoyed their dinner. (I guess they didn't care if the kid ate or not!) The lovely Mrs. Jones (Vita) and I informed him that he wasn't allowed to save seats, and we promptly sat down. A few minutes later, his father showed up with a "gaggle" of people whom he was trying to put on the dog for, and of course, he raised he## with us. We smiled and once again informed him that the theatre was nearly full, and he was welcome to tell ships personnel that we had sat in the seats his son had "saved" for him. He decided against it, but it's a shame that some people are so self centered!
See you aboard,