Recital 37

1 A group of undertakings should cover a controlling undertaking and its controlled undertakings, whereby the controlling undertaking should be the undertaking which can exert a dominant influence over the other undertakings by virtue, for example, of ownership, financial participation or the rules which govern it or the power to have personal data protection rules implemented. 2 An undertaking which controls the processing of personal data in undertakings affiliated to it should be regarded, together with those undertakings, as a group of undertakings.

This recital of the General Data Protection Regulation clarifies article 4 GDPR (Definitions).*
* The reference between articles and recitals is based on the professional assessment of activeMind.legal.