I was going to make a joke about how you’re getting older, but that immediately backfires as I’m always going to be older than you! At least we can make fun of each other as we grow old together!
Happy birthday to my younger sister who a lot of people think is actually my elder sister!
I’m sure it’s only because you’re so wise and mature that people think you’re older than me anyway, sis! Either that or I just seem super young and immature!