If I remember correctly, Indian astrology and Western astrology look at the heavens in very different ways. I found your post very interesting, as we usually think of Sun signs, and not elemental correspondences when we are looking at relationsips of any kind.
From the Western astrological point of view, we could look at the Sun sign compatability as a general way of looking at relationsip and compatability, and follow that up with doing a complete chart comparison to see in what areas there is compatability, and in what areas there will be stress.
This is quite an interesting use for astrology, because we can use it for family relationships, personal (romantic) relationships and business relationships.
Yours was quite an interesting psot!