Common:
* Birthday twin: Someone born on the same day as you.
* Evil twin: A twin who is wicked or malicious.
* Identical twin: Twins who look exactly alike.
* Long-lost twin: A twin who was separated in childhood and later found.
* Siamese twin: Twins born joined together at some point on their bodies.
Less common:
* Arm-twin: A close friend (informal, humorous).
* Brain-twin: Someone who shares your thoughts and opinions.
* Soul-twin: Someone you feel a deep connection with, like a soulmate.
* Spirit twin: A twin who shares your personality and values.
* Twin bed: A bed intended for a single person, but smaller than a full-size bed.
You can also create new compound words by combining "twin" with other words:
* Dream-twin: A twin who appears in your dreams.
* Shadow-twin: A twin who seems to mirror your actions.
* Time-twin: A twin who lives in a different time period.
Let me know if you'd like more ideas!