Also, why is it that verse 14 specifically mentions spouses and children that can be enemies to us? Why doesn't it mention other relatives like parents, siblings, etc. or even friends?

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Verse 14 was revealed on a person called “ awf ibn Malik ashja”

The reason for the revelation is that his children and wife wouldn’t allowed him to respond to the invitation of the prophet to join the Muslims in the battles. He then complained to the Holy Prophet and as a result the verse was revealed.
Generally speaking, your children and your wife are the most closet to you and you can be tested by someone close you then the others.
Not to say others are not tests. Allah knows best and that’s His wisdom