Appleid & ICloud

I need some help with ICloud and maybe

Appleid. My wife and I both have IPhone 12’s and IPad’s that are new this year.

I was trying to set up Photo sharing for these devices but was only partially successfuk,

We each have our own Appleid’s. My two devices and her IPad were successfully

set up but her IPhone was not. If I look at my ICloud account my two devices and

her IPad are there – her phone is not. I have compared every setting I know of

on all these devices and see no obvious differences. This left me with the

following question(s),

For photo sharing to work must all devices be set up under

the same Appleid? How come her IPad shows up in my ICloud Account when she has

a different Appleid?