You've got just one egg
You're not going to make an omelette
Flying just one way
You're not going to make a jet setSister, brother, wherefore are thou?
No need for bunk beds in my bedroom, nowOh, damn you, dads
Why did you settle for only me?
I'm an only child
More than enough for them, but not enough for meOnly child, only child, only child
The only berry on my family tree