How can I add older iPhones to my Apple Music Family Sharing?

I have an apple music family sharing account. I have several older iphones that belonged to my husband that I hoped to use to stream music in different locations. Those phones are registered to him and had his phone number associated with them and he now has a new phone. If I share with him, it will go to his new phone, not to the old ones. How do I add those older devices to my family sharing? I was able to add my old iphnes because they are in my name. I have his apple login, but can't figure out how to do it.

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