No. Righteous Brand grants a power bonus. Bonuses of the same type don't stack. You could still give two different allies the bonus, but granting the bonus to the same ally a second time is pointless.If you strike your enemies twice in a turn with Righteous Brand(using Polearm Gamble and Heavy Blade Opportunity), can you add the bonuses and apply to a single ally?
Well, they don't stack but I wouldn't say it's pointless.
Since the one from the OA ends at the end of your next turn from when you took the attack (ie, right away after your action) while the one you take on your normal action ends at the end of your next turn (a turn away).
They both end "at the end of your next turn." If you take your turn on initiative count 5, then make an OA on count 2, "your next turn" is still the following turn's count 5.
And when it's round 2 count 5 and you go 'Hey, my OA hit so I already righteous branded so my friend on init count 4 gets his power bonus to hit'... you're wrong. You need to hit it again to give it to him, because the OA provided bonus is ending on Round 2 Init 5, and if you hit him now it'll go til Round 3 Init 5.
Wait, let's put some names to the numbers.
Jozan rolls a 17 for initiative. The hobgoblin rolls a 12. Tordek rolls a 3.
On Jozan's turn (round 1, count 17), he hits the hobgoblin with Righteous Brand. It will expire at the end of Jozan's next turn (round 2, count 17).
On the hobgoblin's turn (round 1, count 12), he provokes an OA. Jozan uses Heavy Blade Opportunity to his him with Righteous Brand. It will expire at the end of Jozan's next turn (round 2, count 17).
Now it's Tordek's turn (round 1, count 3). Both of Jozan's Righteous Brands are still in effect, providing Tordek with two (non-stacking) power bonuses on his next attack.
If they did stack, it wouldn't be pointless, because neither one has expired by the time Tordek attacks...
-Hyp.