In previous events, the Leeds siblings have timed their runs together to produce a photo finish, and it was unknown whether they would do the same at London 2012.
But with younger brother Jonathan suffering a 15-point penalty for mounting his bike too early in transition one, Alistair, 24, took the lead and raced away with eventual silver-medallist Javier Gomez.
"We hadn't really thought about crossing the line together too much, just because so many things can go wrong," said 22-year-old Jonathan.
"Competition in triathlon is really good at the moment, as shown by Javier Gomez, so we didn't think about it.
"If we were neck and neck for gold and silver we'd probably think about it in the last 50 metres, but we wouldn't cross the line together and would probably race it out."
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