From the Marketplace, go ahead an click on your name from the top right corner, and then under the "Login as" title, select the member's account on which you would like to login to.

You will therefore be able to control your relationship's account.
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​From your Profile, click on "Login as" > Select the relationship you want to access > Click on "Confirm".

Once logged in to your relationship's account, you'll able to switch back to your account by clicking on "Return to my account".

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