When you're an aunt or uncle, your bigger sibling pays attention to the baby instead. Back in the day, when you used to get all their attention, is long gone. All those glorious days when you were the best baby ever, now you downgraded to second best. And you get in trouble and the baby doesn't. And they tell you to clean up but the baby doesn't. So, then instead of pretending to get married, you have to play aunt or uncle. And make your valentine your sibling. And when you used to be able to play good games, you have to play that horrible game every day.
Then, the sibling yowls when you break something. But if the baby breaks something they let it pass. Then you feel upset because you get scolded for breaking stuff. Then when the baby eats up all the snacks it gets no scolding, but if you eat up all the snacks you get a big scolding and a time out and no snacks the next day. So being old is hard.