retain (something) over (someone or something)
To hold onto or continue to have control, power, influence, etc., over someone, something, or some group. I'm stepping away from the day-to-day business of the company, but I still retain control over any major decisions. I know Sarah's mother retains a lot of influence over her, even though they live in different parts of the country.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
retain something over someone or something
to keep or maintain something, such as power or control, over someone or something. Tony found a way to retain control over Fred. I wish to retain veto power over the committee.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.