So I had this problem the other day where I kept on getting pairing requests from my friend’s bluetooth keyboard. This was rather annoying as the pairing dialog kept on popping up every few minutes. So I googled around a bit and found the following solution which worked for me.
Turn your bluetooth off. This will disable your bluetooth mouse and keyboard and hence you will have to use the built-in ones.
The problem is that at some point the keyboard that is nagging you to connect would have connected to your laptop. Your laptop remembers this and hence accepts incoming pairing request prompting you to verify it.