Yes it picks one instance, the one with lowest UID. If you don't add a 'for each family' then what this event is saying is - I am true if the family object with the lowest UID is this distance from the player, then if this is true, apply the 'actions' to every instance of family. It picks only the one instance of family, with the lowest UID and compares the distance, if it's true then it runs the action against all family members since nothing was initially picked. If false i.e. the family object with lowest UID is outside that distance then nothing will happen.