This is exactly how I came to be the owner of my 8 year old cat, Leo. My friend found kittens almost exactly like that in that scenario; in the middle of no where, in a paper bag, half starved and just babies. The mother was with them so they were probably abondoned. That is so great of your aunt to take them into custody. I have such a passion for animals and helping to prevent abuse and seriously it's people like them who make it possible! Honestly, all you can do is your best to keep them safe and get them to be sold ASAP. You will probably not be able to sell them (hand them over to the buyers) until they are atleast a couple months old and have their eyes open (I remember I wasn't able to pick up my kitten until he was about that age). But I would definitely start advertising it. Since the mother is not there that could be hard on them and like I said the best you can do has already been done. If you keep them nourished and warm they could be ok. However, I know it may be hard to survive without their mother and since they are so young. I believe it would not be hard AT ALL to get these kittens sold, it's the older cats that are always so hard to be adopted. Get ahold of adoption centers for these types of animals to see if they can help. Your best bet would be to try and sell them yourselves if you have the patience and time.
Good luck to you and your aunt!
P.S they are adorable