Piece of advice: Pass the object in concern's UID through the function as a parameter.
This will allow you to always pick the correct object, no matter the family, conditions, etc.
Example:
Family "hittables"
Members:
Player Sprite
Enemy Sprite
Event:
On bullet collides with "hittables" -->
Call function "bullet hits something"
Pass parameters: bullet.damage, hittables.uid
On function "bullet hits something" -->
Condition:
Pick "hittables" by UID function parameter (1) (or function "bullet hits something" parameter hittables.uid") -->
Substract parameter bullet.damage from hittables.health
Destroy bullet