“I told my boyfriend to close his eyes and open his mouth (I was surprising him with candy), and he just did it with no suspicion at all. People with siblings can’t trust like that.”
“My friend jokingly threw a tea towel at me and I let is land on me. She said that was classic only child behaviour to not instantly throw it back and try to hit her with it.”
One huge difference I see time and time again with those who have siblings is that they had much more exposure to a longer timespan of media/music/games growing up.
Right away I realized I do that, but my partner who grew up with two sisters tells me where he’s about to go when he moves, even if it’s to the bathroom.
“My boyfriend is an only child and the giveaway was his confusion at how I can be mad at my sister (who is also my roommate) one minute and turn around and get ice cream or go see a movie together.”