How to unforget a Bluetooth device on an iphone?

Because me and my brother have the same speakers I got my phone to forget what I thought was his but was actually mine and I don't know how to un forget it. Help

Added (1). I can't it doesn't show up when I search for Bluetooth devices

Pair them again.

Usually if one phone is paired with a Bluetooth device then no other device can be paired with it simultaneously, I know it sounds silly but make sure the device isn't paired with your brothers phone and then try looking for it again with yours.

I know you said you can't but this might be of some use.