When you’re in a Family Sharing group, you can share your Pro subscription with other family members.
Here's how:
Go to your iPhone's Settings > [your name] > Subscriptions.
Do either of the following:
• Share all new subscriptions: Turn on Share New Subscriptions. When you purchase a new subscription that’s eligible for sharing, it’s shared with your family members by default.
• Change the settings of your 1SE subscription: Tap 1SE, then turn Share with Family on or off.
To see which subscriptions you’re already sharing, go to your iPhone's Settings > [your name] > Family Sharing.
Check out Apple's Help Article on how to share subscriptions with your family here.