NCR and BOS peacefully

[HausSex]

Hello i was wondering is there any way to make them peace? Because i'm fans both of them and besides that them strong faction.

[ToJKa]

Yes. You must complete the "Still in the Dark" quest for BoS and keep McNamara as the elder. Then when NCR sends you to destroy them, tell that to McNamara and he sends you back with a truce offer. You lose some favor with the NCR, but not enough to matter.

[HausSex]

And will them help NCR protect dam from legion?

[ToJKa]

Yes,  there's some BoS soldiers at the dam fighting the Legion during the final quest.

[HausSex]

And is that possible to make another faction besides BOS to help NCR on the battle? For ex BOS and Boomer helping NCR in battle? Or there of them help ncr? I was wondering.

[ChancellorKremlin]

The Boomers have a quest to help the NCR with the Bomber at the bottom of Lake Mead, and the only thing you can do with the Khans from the NCR angle is have them leave and not fight for the Legion, again, with their own quest. You need to actually go to those places and talk to those people to figure out what to do though.

[gregathit]

And is that possible to make another faction besides BOS to help NCR on the battle? For ex BOS and Boomer helping NCR in battle? Or there of them help ncr? I was wondering.

 

All your answers and MUCH, MUCH MORE are right here: http://fallout.wikia.com/wiki/Fallout:_New_Vegas_quests