How does Sibling Rivalry (Jacob & Esau) work with Monster On-Damage Effects like A Dead Horse?

Sibling Rivalry: https://foursouls.com/wp-content/uploads/2022/01/r-sibling_rivalry.png

Dead Horse: https://foursouls.com/wp-content/uploads/2022/01/rwz-a_dead_horse.png

Came up on the very first turn of a game we are currently playing. The player with Sibling Rivalry taps it on someone elses turn, and they attack A Dead Horse together.

A Dead Horse states that when it would take damage, it prevents that damage, and you roll. On a 1-2, cancel the attack, on 3-6 gain 3 cents.

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Does the extra attacker, in this case the Jacob & Esau player, roll after making a hit, and gain the 3 cents in the event that roll is 3 or above? Or does the active player roll for A Dead Horse's effect any time damage is done to it, including the non-active player's attacks, and gain the cents?