can I share with a grand child that has an iPhone

Hi ibnan,

welcome to the Apple (user-to-user) Community.

Re: can I share with a grand child that has an iPhone : apple music : i pay for apple 1

Seems the "Related Article" above your question has the answers.

ie: Apple One Family and Premier plans, and also Apple Music family subscription can be shared.

while:

Individual subscriptions to Apple Music, Apple One can not be shared

All the best :-)