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Exhibit 21

SUBSIDIARIES OF NISOURCE INC.

as of December 31, 2025

Segment/Subsidiary                             State of Incorporation

COLUMBIA OPERATIONS    

Columbia Gas of Kentucky, Inc.    Kentucky

Columbia Gas of Maryland, Inc.    Delaware

Columbia Gas of Ohio, Inc.    Ohio

Columbia Gas of Ohio Receivables Corporation    Delaware

Columbia Gas of Pennsylvania, Inc.    Pennsylvania

Columbia Gas of Pennsylvania Receivables Corporation    Delaware

Columbia Gas of Virginia, Inc.    Virginia

NiSource Gas Distribution Group, Inc.    Delaware

NIPSCO OPERATIONS

Dunn’s Bridge I Solar Generation LLC    Delaware

Dunns Bridge Solar Center, LLC    Delaware

Fairbanks Solar Energy Center LLC    Delaware

Gibson Solar, LLC    Delaware

Indiana Crossroads Solar Generation LLC    Delaware

Indiana Crossroads Wind Farm LLC    Delaware

Indiana Crossroads Wind Generation LLC    Delaware

Meadow Lake Solar Park LLC    Delaware

NIPSCO Accounts Receivable Corporation    Indiana

NIPSCO Holdings I LLC    Indiana

NIPSCO Holdings II LLC    Delaware

Northern Indiana Public Service Company LLC*    Indiana

RoseWater Wind Farm LLC    Delaware

RoseWater Wind Generation LLC    Delaware

CORPORATE AND OTHER OPERATIONS

Bay State Gas Company    Massachusetts

Generation Holdings I LLC    Indiana

Generation Holdings II LLC    Delaware

Lake Erie Land Company    Indiana

NIPSCO Generation LLC    Indiana

NiSource Corporate Group, LLC    Delaware

NiSource Corporate Services Company    Delaware

NiSource Development Company, Inc.    Indiana

NiSource Energy Technologies, Inc.    Indiana

NiSource Insurance Corporation, Inc.    Utah

* Both Gas Distribution Operations and Electric Operations