Yes, twin is a Scrabble word!
...and is worth 7 points in Scrabble, and 8 points in Words with Friends
twin
Verb
1. Duplicate or match
2. Bring two objects, ideas, or people together
3. Grow as twins
4. Give birth to twins
Adjective
1. Being two identical
Noun
1. Either of two offspring born at the same time from the same pregnancy
2. (astrology) a person who is born while the sun is in Gemini
3. A waterfall in the Snake River in southern Idaho
4. A duplicate copy
What Scrabble words can I make with the letters in twin?
3 Letter Words
2 Letter Words