How are EV shared between both Pokémon during a double battle? For example, if two Pokémon beat a Graveler in double battle, will each receive 2 defense EV, will it be halved and each will get 1 defense EV, or how does it work?
Unlike experience points, EVs are not divided among Pokémon. Any Pokémon that earns experience points from a battle, whether it be from actually making an appearance in the battle, or by simply holding the Exp.Share item, will earn a full share of the EVs earned in battle. So therefore, in the situation that you described, both Pokémon would earn 2 Defense EVs.
Best Ruby/Sapphire Moderator!!
TPM Awards 2004, 2005, 2006
Winner of 2007 Unown Award N & 2008 Unown Award C!!
Chicoslavocia's Revenge is my best bud on TPM!!
Visit her Oekaki Board!!
That's right. Experience points are so numerous that you can divide them between Pokemon by rounding down and not have to worry about losing an excessive amount of points. But imagine your distress if you used a total of three Pokemon to beat that Graveler and found that, since its 2 Defense EVs divided by 3 was less than one, none of your Pokemon earned anything! That's why such stats can't really be divided, because the numbers are just too small to last through such divisions.
To explain further...
Assume that you earn 999 experience points from defeating a certain Pokemon. But you use two of your Pokemon to do it. Therefore, the experience is divided between them.
999 points / 2 Pokemon = 499.5 points for each
But since you can't earn a fraction of a point, each Pokemon only gets 499 experience point. You've only earned a total of 998 experience points between your two Pokemon, but do you really care about the 1 experience point that you lost? Probably not. 1 point out of 999 isn't really that much.
If it worked the same way with EVs, though, you could have a problem. For instance, an Aggron yields 3 Defense EVs. But what if you used two Pokemon to defeat it?
3 points / 2 Pokemon = 1.5 points for each.
But since you can't earn a fraction of a point, each Pokemon would get only 1 point. So instead of earning 3 total EV points, you only earn 2. Do you care about that lost point? Probably! You've just lost a very significant portion of the EVs that you would have earned.
And that's why with EV totals, each Pokemon earns the full amount. For instance, in the Aggron example, each Pokemon would earn 3 Defense EVs rather than 1.
Macho brace's effect would still apply, I believe. The only real difference between single and double battles, as far as the awarding of points is concerned, is that you have to use at least two Pokemon in a double battle whenever possible. But it works in the same way as if you had used two Pokemon back-to-back in a single battle.
So, yes, you should get 6 Defense EV points from that.