I Have A Two Month Old Kitten Who Got Very

I have a two month old kitten who got very sick. he was taken from his natural mother and nursed by her sister who already had kits of her own that were two weeks older. she has not nursed him for more than two weeks now. I have been keeping him alive by bottle feeding him water and cat milk, he is also eating high quality kibble in small amounts. He was very wobbly at first now much less so but now he is constantly turning in circles. What does this indicate and what can I do to help him get better?