First of all, I would wait until both are at least 8 weeks old. 6 weeks is barley weaned and not really ready to leave the breeder. I would want them to have been weaned for about 2 weeks before you take them home. There is just a better chance of survival and they will be more used to only having solid foods at that point. Some breeders loose kits that are 8 weeks due to digestive problems.
Young rabbits do tend to get along. The trouble comes when they mature. As both breeds are on the small end of rabbits, they will mature at about 4-6 months. So they could fight and become territorial at that time. Females tend to be more territorial than males. You might also have to deal with them being mis-sexed and possible litters.
You can put them together and see if they get along. You should be in the area with them and there should be enough space from them to get away from each other. An x-pen will work. Have somewhere to put one of them if they do not get along right away.
There is a chance that even if they get along now, they will not get along later. Getting both spayed can help, but that shouldn't be done until they are about 5-6 months. You can just wait until both are fixed before you try to bond them.
