Is Halo reach multiplayer possible between xbox one and xbox 360?

the xbox 360 version on xbox one can cross play with the 360 but halo mcc or gardians then no. be warned though that the 360 versions of halo will have there servers shut down next december.

As Smwutches already said, Xbox One versions of games can't play Multiplayer with Xbox 360 versions of the game.

However, since the Xbox One is gradually getting Xbox 360 backwards compatible titles, some original Xbox 360 games can run on the Xbox One, and then the Xbox 360 and the emulated Xbox 360 games on the One can play together.

FIFA 16 and 17 are NOT backwards compatible games, so they don't work across Xbox One and Xbox 360.

Forza 5 and 6 don't exist on the Xbox 360. Forza 5 and 6 doesn't work with the Xbox 360 Forzas 2, 3 and 4.

Later this year, the Xbox 360 Halo games will be made backwards compatible (there has not been a set release date yet). But currently HALO: REACH works on the Xbox One already, so your sons could at least play HALO: REACH with each other.

And as Smileskybird said, in the (not too distant) future, Minecraft should allow cross platform multiplayer. But currently it's not possible.

So to sum it up: Check this list here for games that your kids can play together on the Xbox 360, and the Xbox One through backwards compatibility:

http://www.xbox.com/xbox-one/backward-compatibility/available-games

Something as close as possible to Halo 3s multiplayer and Halo Reach's campaign.

No, there is no cross platform multiplayer between the Xbox 360 and the Xbox One.

From Microsoft Xbox UK marketing manager Harvey Eagle;

"Because of the different architecture of the systems it's not possible. Your Xbox Live account on 360 will carry over to Xbox One. That same account will work on both platforms. The multiplayer won't," Eagle told Videogamer. The Xbox 360 is built on PowerPC
architecture, while the Xbox One utilizes an x86 chipset – so no purchased games will transfer to the new system."

Are you trying to system link between Xbox ones that are playing the Halo: Master Chief Collection and Xbox 360s that are playing the Xbox 360/Xbox Original versions of those games? I'm pretty sure that cross-play between Xbox One and Xbox 360 versions of
the games will not work. You can cross-play with the Xbox 360 version of the games on both consoles, for example, Halo 3, Halo 3: ODST and Halo 4 are backwards compatible on Xbox one.

You will either need all Xbox ones playing the Halo: Master Chief Collection or all Xbox 360s running the Xbox 360 Halo game of your choice.