I don't think about twin names very often, I guess they must not interest me too much. But, I like the idea of very subtle themes.
Like
Leo &
Norma, both names of constellations.
Some anagram pairs make me happy, like
Diana &
Aidan,
Alice &
Celia,
Amy &
May,
Darlene &
Leander,
Dolly &
Lloyd. The anagram thing is a major GP idea because philosophically I'm not sure I agree with it (the idea that they are the same person, just rearranged).