Can I put a 10 pound rabbit with a 5 pound rabbit?

Two problems with your idea. First and foremost is that unless 2 females are both spayed, they aren't going to get along. They will likely fight and possibly even to death. Bonding rabbits requires them to first be spayed to rid them of those hormones that prevent bonding. You can read up more about that here:

http://rabbitsindoors.weebly.com/bonding-bunnies.h...

If both rabbits are spayed, then size makes no difference when it comes to bonding.

The second problem is the hutch itself. It is far too small for one rabbit, let alone two. You can learn more about that at the linked video.

The House Rabbit Society recommends a minimum of 24 square feet of run space (though 30 or more is better). The cage you have pictured doesn't even allow for your rabbit to fully stretch upward, nor does he have room to binky or get any exercise. It simply is far too small.

So for bonding info, see the rabbitsindoors site. For hutch info, see the video.

http://www.youtube.com/watch?v=_vvlb-prX4I&feature...

The lower storey needs to be extended into a full run. The lower level doesn't have enough room to run about or jump around in. It's cramped for one, let alone two. With a large run, two rabbits will be fine, although the sleeping area is too small so the food may need to be placed on the lower floor, with the entire upeer level for sleepping.