Is it odd to grieve over someone you didn't know personally?

A friend of my family's just died a couple days ago in a sudden accident near me, due to a failing emergency brake. I had no clue about it until today, nor did they. It's hit me hard even though I didn't know the guy personally, maybe because I've experienced a similar incident with a family member (except that one's alive), or it's because I knew he was a kind person to my family. I don't know.
Is it odd to grieve over someone you didn't know personally?
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