Jo Johnson, the brother of Boris Johnson, has indicated he's stepping down as an MP and minister - claiming he's "torn between family loyalty and the national interest".
The Conservative MP and minister of state made the announcement on Twitter.
He said: "It’s been an honour to represent Orpington for 9 years & to serve as a minister under three PMs.
"In recent weeks I’ve been torn between family loyalty and the national interest - it’s an unresolvable tension & time for others to take on my roles as MP & Minister."
It was not immediately clear whether the decision will take effect immediately or after a widely expected general election in the coming weeks or months.
47-year-old Jo Johnson has served as an MP since 2010.
He's served in a number of ministerial positions, and was made minister of state for universities when his brother became prime minister in July.
While not a senior minister, he does attend cabinet meetings.
Unlike his brother, Jo has expressed concerns about Brexit and has previously called for a second referendum with an option to remain in the EU.
His decision to step down is the latest example of upheaval in Westminster amid the ongoing Brexit impasse.
More than 20 Tory MPs have lost the party whip - effectively being expelled from the parliamentary party - for backing an opposition bid to block a no-deal Brexit.
A general election is likely to take place in the near future despite the British government's initial bid to to trigger one failing yesterday evening.
Labour has insisted they'll support an election - but only after the legislation blocking no-deal becomes law.
It's still unclear whether an election would take place during Boris Johnson's preference for mid-October or at a later date.
Meanwhile, former Labour MP Luciana Berger has announced she has joined the Liberal Democrats.
The independent MP tweeted to suggest they're the "strongest party to stop Brexit".
Chuka Umunna - who also quit Labour in February and now also sits as a Liberal Democrat - welcomed his new colleague, saying he's "absolutely delighted".