What does it take to care about a stranger?

“He is more worth to you, perhaps. But the stranger is someone else’s friend and brother. So which life is more important?”
― Madeline Miller, The Song of Achilles

It’s human nature to care about others, namely those that are family or friends. The question is, at what point does a stranger turn into a friend, and cause you to actually reach out or at least try to see from their perspective? In my belief, you need something to happen to someone around you for you to see it’s actually happening, and not just something you saw online. Personal experiences, or ones near personal are the ones that cause people to actually care.