Multisignature addresses aren’t limited to 2-of-3 or 3-of-5. Any combination M-of-N can be used, where M is the threshold of signatures needed to spend funds. This provides granular control over security and redundancy. For instance, a corporation might adopt 3-of-5 for board approvals, or a family might use 2-of-2 to require both spouses’ agreement. Bitcoin’s standard script supports up to 15-of-15, though storing and coordinating that many keys can be impractical. M-of-N is the backbone of advanced custody, forging trustless cooperation between signers.