Well, he's nursing on his brother's fur and his spayed mother's tummy fur
where her nipls are.
Should I worry, separate them or will he grow out of it?  Will this behavior
cause psychological illness in the poor host cat?  The kitty/leech is not
stopped or dissuaded by either the host brother or mother.  Everyone
involved seems to be okay with it except for us human onlookers.  I have
heard of kittens trying to nurse human earlobes, but not each other.  advice
appreciated.