No I don’t see the emails when I sign in to iCloud.
If you see no email in iCloud.com it means you are not using iCloud for email. Whatever is happening is not related to having signed out of your Apple ID. (Besides, signing out of an iCloud account on one iPhone does not affect the other iPhones, iPads, and Macs signed into that same Apple ID.)
So, what are your email providers (Gmail, Yahoo, Outlook.com..)?
It could be as simple as having "Filtered by: Unread" selected on those iPhones - if there's no unread mail, then you'll see nothing in that inbox.
It could also be a matter of whether those iPhones are actually signed in to those mail accounts.
Go to Settings > Passwords & Accounts. Is your email account listed there? If it is, tap on the account. You'll see a message to sign into the account if it is currently not signed in. If it is not listed, then you need to Add Account...