EMOTION

[Kitty]

There is no soul mate sign dude.
There is physical compatibility and emotional compatibility.
And then there is how far into their Zodiac they are, like im at the end of Pisces, I have the Pisces traits but can be very fucking Aries.
A Pisces at the start of Pisces will be nothing like me. Then there is the lessons life has taught you, they change you.
There is however twin flames who when come together they change things all around them not just themselves. And I think you may have many of them there is not just one.
And Leo's are friends of everyone, its just how they are. Its nothing about you.

This is one subject I know really well.

In a natal chart, the 7th house  rules marriage and partnerships which is what I meant by soulmate sign. And depending on the ruler of the house and the planets placed there and their aspects, you can get a pretty good idea. 

Also when looking at synastry, emotional compatibility is the aspect between two peoples sun and moon and physical compatibility is between venus and mars. Lots more indicators too, but those are the biggies.

As far as the subdivision of the signs or decans, yes that is true, but that is a small piece of a much larger puzzle.