If they are the same age and together from day one they can happily share a brooder. We had issues introducing our geese to our 10 ducklings who are a week older. (we got the ducklings one week and the goslings the following week so they are very close in age, but that one week separation...). The ducklings beat up the goslings everytime they were together. We had to supervise their time together because as soon as we would turn out backs the ducklings would attack the little goslings.
When they are older and the geese larger I am sure they won't have a problem.
I put my 5 day old goslings in with my new ducklings from Holderreads and they all got along great. The goslings just didnt care who they walked over when they were getting around. They are all outside now and the all cuddle together. I hope it stays that way too