Same or adjacent sun sign relationships

I'm curious to know whether this just happens to be a phenomenon in my life. A lot of the happy couples I know have got the same or adjacent/neighbouring sun signs.

There might be other reasons why they're all compatible but there just seem to be a whole load of couples in my life that don't have a gap between their sun signs.

I'm in a Capricorn/Aquarius partnership and it works great. I'm the Cap, together over seven years now.

I also know of happy couples (ie the combination seems to work) with:

Both Taurus
Both Libra
Both Sagittarius - x2!
Both Aquarius

Aries F/Taurus M
Gemini F/Cancer M
Gemini M/Cancer F
Virgo F/Libra M
Libra F/Scorpio M
Sagittarius M/Capricorn F

There's probably more that I've forgotten. I reckon there's something in it but what does everyone else think?