RR page 22

If a single occurrence creates multiple triggering

conditions (such as two characters being killed

simultaneously by a claim 2 military challenge), those

triggering conditions are handled in shared interrupt/

reaction windows, in which abilities that refer to any

of the triggering conditions created by that occurrence

may be used.

RR page 17

Unlike actions, which are resolved during action

windows, each reaction may be initiated once each time

its specified triggering condition occurs, as described in

the reaction’s ability text.

Joffrey Baratheon

Reaction: After a Lord or Lady character is killed, Joffrey Baratheon gains 1 power.

A claim 2 military challenge kills 2 Lord characters simultaneously. Can I use the reaction on Joffrey Baratheon twice or only once?

Naturally I would argue for twice, because there are two different triggering conditions. But there is only a single time, in which both triggering conditions occur, so someone could argue for once.

The triggering condition occurs twice. "Time" here does not mean "instant", it means "occurence".