Exhibit (21) LIST OF SUBSIDIARIES OF HSB GROUP, INC. NAME OF COMPANY STATE/JURISDICTION OF INCORPORATION/ FORMATION The Allen Insurance Company Bermuda The Boiler Inspection and Insurance Company of Canada (wholly-owned by HSB Engineering Insurance Ltd.) Canada EIG, Co. Delaware The Hartford Steam Boiler Inspection and Insurance Company Connecticut The Hartford Steam Boiler Inspection and Insurance Company of Connecticut Connecticut The Hartford Steam Boiler Inspection and Insurance Company of Texas Texas Hartford Steam Boiler International GmbH Germany Hartford Steam Boiler (Singapore) PTE Ltd. Singapore HSB Associates, Inc. New York HSB Capital I Delaware HSB Capital II Delaware HSB Engineering Finance Corporation Delaware HSB Engineering Insurance Limited (wholly-owned by EIG Co.) England HSB Haughton Engineering Insurance Services, Ltd. (wholly-owned by HSB Engineering Insurance Limited) England HSB Investment Corporation Connecticut HSB Professional Loss Control, Inc. Tennessee HSB Reliability Technologies Corp. Florida Integrated Process Technologies, LLC (51% owned) Delaware One State Street Intermediaries Connecticut Ra-Hart Investment Company Texas