Charlotte Hogg, a newly appointed Bank of England deputy governor, must take steps to avoid conflicts of interest, say MPs.
Ms Hogg, who became deputy governor for markets and banking in February, sits on three powerful Bank committees.
One of them, the Prudential Regulation Committee (PRC), oversees UK banks.
On Tuesday MPs on the Treasury select committee questioned her about her brother, who works for Barclays as a director in group strategy.
Treasury committee chairman Andrew Tyrie said: "The committee recognise the value that Ms Hogg will bring... from her operational experience in the financial services sector... She will need to put in place arrangements to address conflicts of interest or the appearance of such conflicts."
Ms Hogg will also sit on the Monetary Policy Committee (MPC), which takes interest rate decisions, and the Financial Policy Committee (FPC).
She told MPs: "I haven't sat on the PRC yet. I think it's certainly a possibility that I could recuse myself."
The Bank of England declined to comment.
The BBC understands the Bank already has policies in place for employees to avoid conflicts of interest.
Employees must declare personal relationships, sign up to a code of practice, and recuse themselves from decisions where there is a conflict.