Breach Of Warranty Insurance Are Insurers Liable To Indemnify B If A Breached Warranty On A Combined/joint Policy?

Are insurers liable to indemnify B if A breached warranty on a combined/joint policy? - breach of warranty insurance

If A and B have a common policy, but it was gross negligence and breach of warranty. Therefore, both A and B has suffered significant damage to them. Insurance compensate B? If so, could subrogation rights of insurers exercise? The whole thing is very much appreciated.