Could someone explain to me why NeXT Software/NeXT Computer is listed as a co-plaintiff, on a lawsuit that was only recently filed? Did Apple and NeXT not full

Could someone explain to me why NeXT Software/NeXT Computer is listed as a co-plaintiff, on a lawsuit that was only recently filed? Did Apple and NeXT not fully merge in some capacity? As-is, this would be like reading Attachmate, Inc., Novell, Inc., and WordPerfect Corporation had just sued Microsoft.