Broken Phone - How to reset sons Password

My son broke his SE, needs a new screen. He does not remember his password, so the apple store is unable to fix. Apple store rep said to go in to my family share account, click on my son, and could reset password that way, not true, only his user name showed up, no option to reset. Followed various suggestions online, but all end with a confirmation text going to a broken phone that we cannot access. Saw some suggestions regarding a reset email, have found no way to send that, and if it goes to my sons icloud account, still dont know the passwords.

Any suggestions?

Thanks!