Serve two masters
Definition 1 of 1
Pro Tip 1/3Loyalty Conflict
The phrase often highlights a struggle to stay loyal to two different entities or ideals. 
As a consultant, she found it tough to serve two masters, balancing the needs of her company and her client.
Pro Tip 2/3Metaphorical Use
The phrase 'serve two masters' is usually metaphorical, not about literal service to two different people. 
He couldn't serve two masters, being torn between his career and his passion for art.
Pro Tip 3/3Internal Struggle
It suggests an inner conflict when one has to make a choice between two important commitments. 
She struggled to serve two masters, her family responsibilities and her academic ambitions.