Following in the footsteps of the Gmail app on Android, Gmail on iOS will now let you multiple Gmail accounts into one universal inbox. If you have the left-hand side drawer out, the “All inboxes” option there will, as the name suggests, show you all the emails you get from different accounts in one inbox. Google assures that no emails will be shared between accounts, even with this feature enabled. It’ll be coming to Gmail and G Suite users over the next 15 days.
Source: The Verge