It's called a Bitcoin Fork. I wrote a topic about it years ago, although the values are much lower by now, and most Forkcoins are worthless. But you'll own a few dollars worth of Forkcoins too. Chances are it's going to a be lot of work to recover them from your multisig, so if you don't move them, just keep your multisig in case it becomes worth more in 10 years (which I don't expect to be very likely).