I have a moma cat who had kittens about eight months ago. She had three and we kept them all. Moma cat recently had another litter but sadly these babies didn't make it. She rejected them. In the last 2 weeks moma cat has started nursing the older kittens that were born about 8 months ago. Is this normal or will this hurt the moma cat? The kittens are as big as moma is and so it looks funny when we find them nursing.