@Joannesalfa, that's why I suggested he use max(0,PlayerAttacks.Damage-Enemies.Armour). That will never remove less than zero hitpoints.
MustacheGolem, you need to set the family itself to have those instance variables - that's the beauty of families. That way, anything within the family gets its own instance of that variable. So, your enemies family itself could have hitpoints and armour, for example, but when you put each enemy on the layout, you can specify individual hitpoints and armour values for each.