What are the genetics of Purple Kush

I'm a budtender and we just managed to get our hands on some Hindu Kush and as I do, I was researching it and i found OG Kush and Purple Kush are children strains to Hindu Kush. That's where i get confused though because my sources say Purple Kush is a cross between Purple Afghani and Hindu Kush. Though when i look into Purple Afghani it says its a cross between Purple Kush and Afghani.

That's where i find a bit of a feedback loop. If Purple Kush is Purple Afghani's parent, how is Purple Kush also Purple Afghani's child? Sorry if I'm misunderstanding something, thank you!!