We can see in the place called Gethsemane when Jesus was praying an angel came to strenghten him ! <22:43 Then an angel from heaven appeared to him and strengthened him.> also in the book of Hebrews 1: 14, < Are they not all ministering spirits, sent out to serve those who will inherit salvation?> GOD is talking about angels here, and what's sure is that every Believer (Christian) has his own Guardian Angel. For GOD loves us so much that HE makes sure that we have a singular Angel Bodyguard. So the response is NO ! Different People can't have the Same Guardian Angel !
concerning the unbelievers, i don't know if they got a guardian Angel, but what it's true and i must say it again for Christians < Angels are spirits sent out to serve those who will inherit salvation> Heb 1:14. That means you, Me She, He! have a singular Guardian angel, not for a group of people an angel.
I hope u gonna find ur answer ! May God bless U !