Totter backwards, avoiding a married uncle or brother (5)

I believe the answer is:

remus

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'brother' is the definition.
(mythical founder of Rome with his brother Romulus)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for remus that I've seen before include "Legendary founder of Rome" , "Twin of Romulus" , "City founder - "uncle" storyteller" , "US relative who did accounts" , "J. C. Harris's storyteller Uncle" .)

I've seen this clue in The Times.

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