Older cat sometimes grooms younger one

I have two cats, Lucy is the older and have had her almost two years, although she is almost five years old. Oscar is almost a year old. Lucy doesn't really get on with Oscar, however she will tolerate. They won't play together and Lucy will hiss at him if he tries to join in her games.

She will sit next to him sometimes and they are happy to sit in the same room as each other. Oscar doesn't really have a problem with Lucy and tries very hard to get close to her to play or cuddle.

Although sometimes Lucy will give Oscar a few licks on the head and ears, which Oscar seems to really like and will push his head towards her for more, but after a few licks she will hiss and sometimes swat at him.

Anyone have any idea why sometimes she grooms and then hisses? I find this very interesting and would love to hear some replies.

Thank you all

Clare

Years ago I had two cats, Sasha and Peppy. Sasha was the dominant cat. She would sometimes lick Peppy's head and once she was finished she always bopped Peppy on the head. I have no idea why she would do it though I suppose it was to make sure Peppy remembered who was in charge.

It's actually just instinct for the females to do this. Even a mom cat with her kittens will sometimes perform her duties and lick her kittens, and when she feels they have had enough, she will nibble them or paw them away from her.

Yea, Niko will do that with Isis. Isis will come up with to her and lay beside her, snuggling as close as possible, and Niko will not mind. After awhile she'll clean Isis up and then suddenly BOP! right on the head with a big paw slap. Isis then proceeds to bound away with her big kitten feet.

Silver will go up tp Midnight and head bump him under the chin, looking for some grooming He usually grabs her around the shoulders with his arm (Like a head lock, LOL!) and grooms her roughly, then gets in a little nip! She seems to like this, as she comes back for more all the time!