2 Apple Watch ( 2 Different person ) one Iphone 15 P

You can have 2 watches on 1 phone for personal use, I have my old SE that I use when swimming and my daily driver series 9

But, if hou want to have this for a family member you'll need to set it up as a family member watch: If you don't do that this family member needs to be near your iphone and will get your notifications

See this link to instructions on how to set up a watch for a family member, and this is mostly meant for a kids watch

Set up Apple Watch for a family member - Apple Support

Apple Watch Family Plan

Set up Apple Watch for a family member - Apple Support

Set up Apple Watch For Your Kids - Apple Support

Some limitations: Cannot receive SMS/MMS messages, as that depends on a fully paired iPhone. Messaging is pretty much limited to Apple’s Messages, unless the messaging service provides an Apple Watch app. Alarms, alerts, notifications on the iPhone are not sent to the Apple Watch. Apple Pay via a credit card is not available. Also not available: Medications, respiratory rate, irregular heart rhythm notifications, ECG, AFib History, Cycle Tracking, Sleep, Wrist Temperature, Blood Oxygen, Walking Steadiness, Audiobooks, Camera Remote, News, Shortcuts, and the double tap gesture.

Also check this related article, to avoid mixing up your workout and health data, in case you do not set up the second watch for a family member, as mentioned above.

Set up more than one Apple Watch - Apple Support