Inconsistency: Zombified piglins are not considered zombies

Zombified piglins are not in the zombie family, despite behaving similarly to them.

Steps to reproduce:

1. Spawn a zombie, husk, drowned, zombie villager, and zombified piglin.

2. Run the following command: /kill @e[family=zombie]

Expected results:

All of them die.

Actual results:

The zombified piglin remains.