If Newt was in heat during this interaction then it is completely normal. Yes, even at 14 weeks. It may continue after they are both fixed as well as some cats just continue the actions even though nothing will occur.
If you are truly disturbed by it may I suggest getting the kitten a large stuffed animal to hump. It may help. Although I would suspect that is going to be the last you'll see of it if Newt is being spayed today.
I would not worry about getting Newton fixed at five months. He will be fine to wait till the original date.
Assumptions do nothing but make an ass out of u and me.
We can stick our heads in the sand for only so long before it starts choking us. Face it folks. The pet population is bad ALL OVER THE WORLD!