"Is a bear like a man?"

Exactly. The idea of a jealous, murderous relationship between two siblings is common enough that we can imagine it arising spontaneously in many cultures. That Wiki was very interesting because it showed that this motif was even more widespread than I imagined.

But just because two things have a superficial similarity doesn't mean they have a common origin (e.g., bears, men) Maybe the key thing to focus on is the tell-tale musical instrument because that seems to distinguish the main variants.   

Are there other common folk songs that don't involve murderous siblings but DO involve tell-tale musical instruments?