Faithful signs and aspects in the natal chart

Indicators of someone's capacity for faithfulness when looking at their horoscope:

Earth heavy charts: "I don't want to waste this relationship"
Most personal planets in capricorn, taurus or virgo - see above
Most planets in fixed signs: If you look at someones chart and they have most planets in Scorpio, Leo, (Aquarius) or Taurus, and no uranus, this person is probably a keeper. They are the ones who marry their high school sweethearts and stick with them for life.
Moon in taurus, virgo or capricorn *
Venus or mars in virgo/taurus/capricorn*
planets in the 8th house*:
(*unless in aspect to uranus)
Saturn types
Sun saturn, moon saturn, venus/mars saturn (*unless in aspect to uranus)
These people will cling to established relationships. Til death do you part. They may find it hard to show affection/splurge on you however, even though they love you.
In general, earth signs in personal planets are faithful, more out of laziness, conservatism and a need to build solid foundations, than anything. Unless there are aspects to uranus, security is a big need for these signs. Throw some Uranus in hard aspect (conjunction, square, opposition) to personal planets (sun, moon venus mars and to some extent, mercury)in any natal chart and all the security stuff goes out the window, but you won't know when where, or why.
Building things of value and sticking to them comes naturally to earth signs. Taureans are known for not giving up and being stubborn. The hardest thing for a moon in capricorn/taurus/virgo to swallow is to know that all the effort they put into building the relationship was wasted. Once these people have dedicated themselves to a relationship, they generally won't move, because they just can't. The longer it lasts, the less likely they are to leave. If you cheat on one of these signs, they will be most likely to stay with you after the initial "shit hits the fan" stage, because they are comfortable with routine more than anything.

Scorpio types: "You are the only person I want to be with" 
Generally faithful. For different reasons than the earth signs, that is emotional security. The only thing is that they are intense and require so much devotion and loyalty. Many get scared by all the intensity of it and want to run away. However, if you are into passion and intensity then, perfect.
Scorpio sun, moon, venus, or mars (*unless in aspect to uranus)
Moon-pluto conjunct, square, opposite. Because their emotions are so intense, they don't enter relationships lightly. Emotional ties are heavily invested and hard for them to sever.  

More later!