For astrology, understanding relationships in the horoscope (knowledge of the sky's photograph at a specific moment) is fundamental to knowing the possibilities of understanding between two people. In astrology, this knowledge is called synastry. Through a synastry horoscope, we can find common bonds. As a general rule, the most important planets will be the Moon, the Sun, Venus, and Mars.
However, other dominant factors in synastry will be understanding each individual's ascendant. The ascendant indicates what type of personality traits manifest in each person, and therefore how we attract others.
If, for example, we have a Leo ascendant, it will be more likely that we are interested in people who have a well-positioned Sun, or in the case of a man, a woman with the Moon in this same sign.
For a general case, it is important to know the place and sign where Venus is located. In this way, we will gain some knowledge about the type of tastes a person has. For example, we can find a man with Venus in the sign of Gemini with a special interest in an intellectual type of woman, someone who is restless both physically and mentally.
It is also possible that a woman with Mars located in the sign of Aries desires to meet strong-willed men. All of these are general indications; however, once seen in the natal chart, they can give us important clues about the type of person that attracts each one of us.
In a horoscope (a photograph of the sky at a specific moment) in which clear indications are seen of the type of person someone likes, we must also observe the sector of the natal chart referring to stable relationships and partnerships. If this sector contradicts personal tastes significantly, it may indicate that a person is clearly interested in one type for relating to and another for establishing a bond.
In some cases, we also observe factors that can delay or accelerate relationships. We must keep in mind that a natal chart evolves in the same way an individual does. We cannot make the same interpretation for a person aged 19 as we would for someone aged 50.
Understanding the vital moment the person is transiting through is necessary to make a correct interpretation. An astrologer is not a fortune teller; they are based on data that they try to fit into each person's vital moment.