Last year, we fostered several litters of kittens (some with their mothers, some without). We ended up keeping seven of those kittens. Up until they were about 7-8 months old, three of them would "nurse" on Spike (who is a boy and only a couple months older than then!). Spike never minded and he even seemed to encourage them to do it sometimes. I think it was just a "security blanket" type thing.
It could be. Coco had Kittens once and I kept Stormy. She was a very good Mom and everytime I get a new Kitten they try to Nurse on her. Stormy didnt it for over 6 Months. I lost stormy Dec at age 5 from Kidney Failure. Its funny they always go to Coco.
My cat Ree-Ree sucks on Fiona's toes! Can you believe it....and she lets him! He tried going for her nip's but she was absolutely against it....but she let him suckle her toes. It's the cutest thing. She cleans his head while he does it.