British Prime Minister Boris Johnson’s younger brother, Jo Johnson resigned as a junior minister on Thursday, and said he would also step down as a lawmaker. He added that he could no longer reconcile “family loyalty and national interest”, AFP reported.

His resignation came days after the prime minister expelled 21 Conservative lawmakers from the party for failing to support his Brexit strategy, including Winston Churchill’s grandson and a former finance minister.

Boris Johnson had promised to leave the European Union on October 31 with or without a deal, but several leaders across party lines united against it.

In 2016, Jo Johnson had campaigned strongly against Britain’s exit from the European Union, which put him at odds with brother Boris Johnson. However, he accepted a job as a junior minister in the business and education departments when his brother became the prime minister.

“It’s been an honour to represent Orpington [a London suburb] for nine years and to serve as a minister under three prime ministers,” Jo Johnson said in a tweet. “In recent weeks I’ve been torn between family loyalty and the national interest – it’s an unresolvable tension and time for others to take on my roles as MP & Minister.”

“The Prime Minister would like to thank Jo Johnson for his service,” a spokesperson from Boris Johnson’s office said in a statement, according to Reuters.

“He has been a brilliant, talented minister and a fantastic MP [Member of Parliament],” the statement added. “The PM, as both a politician and brother, understands this will not have been an easy matter for Jo.”

The Johnsons were reportedly deeply divided over Brexit. Boris Johnson’s third sibling, Rachel, and their father Stanley also wanted to stay in the European Union. His father Stanley was a committed europhile and former European Commission official, and sister has represented different parties opposed to Brexit.

Jo Johnson, a former Financial Times journalist, earlier quit the then-prime minister Theresa May’s government, after his critique for another referendum to avoid her Brexit plans. He had been an MP since 2010, serving in several ministerial roles.

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