Create dataloader1 for Dataset 1 with batch size 54.
Create dataloader2 for Dataset 2 with batch size 10
Then do something like:
for x1,y1 in dataloader1:
   x2, y2 = next(iter(dataloader2))
   # then concatenate x = [x1,x2] and y = [y1,y2]
   # use x,y for fwd pass and backwd pass
   

Relevant discussion 3