Not Romulus's uncle (5)

I believe the answer is:

remus

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'uncle' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for remus that I've seen before include "Uncle --, US narrator" , "One of the founders of Rome" , "Brother of 15" , "Famous twin" , "Twin of Romulus" .)

I've seen this clue in the Evening Standard.

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