Pairing BCM20730 keyboard with OS X Yosemite

I have a bluetooth keyboard which appears in Bluetooth settings as "BCM20730 Keyboard", which probably means it uses a Broadcom BCM20730 bluetooth IC. Both on my Macbook Pro 13" Mid 2009 and on my iMac it is not pairing. On bluetooth settings, I click on pair, it says "Connecting" and soon it shows a yellow sign with an exclamation mark followed by "Pairing failed". I already tried cleaning the bluetooth .plist, resetting both SMC and PRAM. Also, I can successfully pair the keyboard with my iPhone.