We have a 12 month old kitten and there is an older female cat in the area. This older cat comes around to our house and picks up our cat by the neck, carrying her around. Our cat does not get bitten and does not react to the older cat's behaviour, but is the displayed maternal behavior from the neighbor's cat normal?
Different cats have different levels of the tendency to want to take care of babies. One cat I knew tended to steal kittens from multiple other mother cats in the same household, even after she was fixed. All the kittens from two other litters ended up in one box with her in it. Any cat that has an excess of this nurturing instinct may try to mother (take care of) any kittens or young cats it can find or sometimes even other young animals like puppies or rabbits.