My parent's cats, Sam and Alfie (siblings) are both 12 now, but a couple of years ago, Alfie kept mounting Sam. We found it amusing at first as Alfie is generally the submissive one, but poor Sam started to get quite upset as it was happening at night, and on a regular basis. Eventually we stepped in and separated them, as Sam really was getting distressed.
The mounting episodes decreased over time and eventually stopped. I would recommend intervening if and when Pagan gets quite upset, and if it is happening on a regular basis.
We also tried Feliway but I'm not sure that made much of a difference. Who knows?!
Lynds