My brother updated to iOS 9, then he started getting iCloud keychain verification messages from iMessage ("Your iCloud Keychain verification code is: xxxxxx"). He kept ignoring them till it was just frustrating. When he finally clicked on the link in one of the messages (it was a 6 digit link), it took him to a verification screen. Which seems pretty normal. But what wasn't normal is that my number is the one that was showing up on that verification screen. So when he enters the 6 digits, I get an iCloud keychain verification message with a 6 digit link. I don't click on any links from numbers or emails I don't know.
He ensures me that my phone isn't part of his "trusted device" list. So not sure how this mess started between our phones. I don't have the 2 step verification activated, and he says since he updated to iOS 9 he wasn't even aware of a 2 step verification process. So he hasn't set up his account as such either. Anyone else having this issue?