Why is Saturn the "glue" of relationships in Synastry?

Interesting...

Well Saturn in synastry creates such a strong bond and it's hard to ignore it,if good aspected it can indicate long term stable relationship,even marriage,partners are responsible and loyal,while bad aspected one brings disappointments,limitations,arguments,

emotional coldness and even hate between two people...

Also they say that a lot of Saturn aspects in synastry chart may indicate that relationship is karmic so maybe that's why it's like glue,Saturn aspects can indicate karmic debts and obligations and things that must be learned and overcomed in this lifetime.

Ahh! I guess that's the only way to make relationships work long term. Let people do whatever and have sex with whomever they want, they'd stick to the one they love. Awww.

Not sure if Saturn is a glue but maybe that helps.

For the Moons you can also check reception by... reception by... (dafuck was that called)... basically check if the rulers are compatible in temperament. For example, Moon in Aries and Moon in Scorpio are both ruled by Mars traditionally so they get a certain compatibility (again I can't recall the exact term). Moon in Virgo and Moon in Aquarius, por ejemplo, could be second best. The former is ruled by Mercury and the latter by Saturn (both cold and dry according to traditional analysis).

Antiscion also helps (Aries-Virgo, Taurus-Leo, Gemini-Cancer, Libra-Pisces, Scorpio-Aquarius and Capricorn-Sagittarius are similar to each other in that way). That helps too.

Good luck with the analysis!

Gemini and Cap is like Virgo and Aqua: Mercury + Saturn, both are cold and dry. Gemini is diurnal and Cap is nocturnal though so the former is more pro-active and obvious while the latter is more re-active and hidden.

I read that Saturn with a good aspect to your Moon sign means that you support your partner and have a spiritual connection or something like that.