Nutered cat still humping?

So I have a cat named Booger. He is nutured. He's about seven or eight now. Booger has never been playful for being Persian, just very sweet. But about a year and a half ago I got a kitten. Female named Qui Qui. She isn't spayed yet. She has been in heat many times and Booger has just completely ignored her. But lately Qui has be being jumped on by him, it looks like he is really trying to penitrate her, but sucks at it. She is on her side the whole time and his butt is way up in the air. I'm just wondering if I have anything to worrie about as far as kittens go? She is getting spayed soon though.