Bitcoin’s wild ride has gotten a huge amount of attention. But over the past two weeks, some of its crypto cousins, like litecoin and Bitcoin Cash, have muscled their way into the spotlight.

On Tuesday, for instance, bitcoin-services company Coinbase announced it would list and support Bitcoin Cash, which is an alternative version of bitcoin that launched on Aug. 1. The news sent prices of bitcoin down and Bitcoin Cash skyrocketing.

Plenty...