It could have been mother and child, or just two unrelated ones. The less dominant one may have been biffed out of the way, and would probably wait for the other to leave before eating. Was the smaller one looking a bit bristly or reticent?
Do you have just one food bowl in there? If not, divide the food between two so there are less confrontations.
Now is the time when they are eating alot to build up fat reserves for hibernation. A young one can hibernate at or below 400g, but is unlikely to survive hibernation, so they really need to be 600 or 700g to be safe.
If you are worried about the small one, hijack it (with gardening gloves on) and weigh it.
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