This deserves stressing: if you ever have to recover your multisig wallet you'll need:
  • the required quorum of private keys (e.g. 2 of 3); and
  • the xpub of ALL co-signers, i.e. 3 xpubs in case of a 2 of 3 setup.
People have lost money because they did not properly back-up all co-signer xpubs.