Elladan and Ellrohir are described as twins. The word "twin" might not have been used, but they literally were "described" as twins.

Lord of the Rings > The Return of the King > Book Five > Chapter II The Passing of the Grey Company:

"...and two tall men, neither young nor old. So much alike were they, the sons of Elrond, that few could tell them apart:..."

Also, Lord of the Rings > The Return of the King > Appendix B > The Third Age:

Year 130 Birth of Elladan and Elrohir, sons of Elrond.

Pretty damn explicit. If Tolkien didn't want them to be twins he would have given them different birth years and not explicitly described them as being hard to tell apart. Soooo I think it's super safe to assume that Elladan and Elrohir who were born in the same year, who looked super alike and were never apart were twins.

Elladan and Elrohir are described as twins. The word "twin" might not have been used, but they literally were "described" as twins.

"...and two tall men, neither young nor old. So much alike were they, the sons of Elrond, that few could tell them apart:..."
_{The Lord of the Rings, The Return of the King, Book V, Chapter II, The Passing of the Grey Company}

Also in the Tale of Years, from Appendix B:

Year 130 Birth of Elladan and Elrohir, sons of Elrond.
_{The Lord of the Rings, The Return of the King, Appendix B, The Third Age}

Pretty damn explicit. If Tolkien didn't want them to be twins he would have given them different birth years and not explicitly described them as being hard to tell apart. So I think it's super safe to assume that Elladan and Elrohir who were born in the same year, who looked suspiciously alike, and were never apart were twins.

Years late, but user46509's comment shouldn't go by uncontested.

"Wikia is a crap source. Elladan And Ellrohir are never described as twins in any published work.. – user46509"

The word "twin" might not have been used, but they literally were "described" as twins.

Lord of the Rings > The Return of the King > Book Five > Chapter II The Passing of the Grey Company:

"...and two tall men, neither young nor old. So much alike were they, the sons of Elrond, that few could tell them apart:..."

Also, Lord of the Rings > The Return of the King > Appendix B > The Third Age:

Year 130 Birth of Elladan and Elrohir, sons of Elrond.

Pretty damn explicit. If Tolkien didn't want them to be twins he would have given them different birth years and not explicitly described them as being hard to tell apart. Soooo I think it's super safe to assume that Elladan and Elrohir who were born in the same year, who looked super alike and were never apart were twins.

Elladan and Ellrohir are described as twins. The word "twin" might not have been used, but they literally were "described" as twins.

Lord of the Rings > The Return of the King > Book Five > Chapter II The Passing of the Grey Company:

"...and two tall men, neither young nor old. So much alike were they, the sons of Elrond, that few could tell them apart:..."

Also, Lord of the Rings > The Return of the King > Appendix B > The Third Age:

Year 130 Birth of Elladan and Elrohir, sons of Elrond.

Pretty damn explicit. If Tolkien didn't want them to be twins he would have given them different birth years and not explicitly described them as being hard to tell apart. Soooo I think it's super safe to assume that Elladan and Elrohir who were born in the same year, who looked super alike and were never apart were twins.