In Relationships reading generally I assess these factors.
1. Karaka ( Significator of relationship): Venus is the significator of love, pleasure, romance, and relationship. Venus rules attraction, what kind of relationship, beauty you like or what kind people you attract in your life is seen by the condition of the Venus. Although other factors are involved e.g. if your Venus conjunct with other planet or aspects by some other planet it modifies your capacity of love and relationship. Did you ever observed in your life why you like certain type of people, or why you attracting the same pattern of relationship in your life. This is what we entirely don't understand, this is because of condition of the Venus. So this can be understood by looking at Venus in chart to see how we approaches, views, handles love and relationship.
2. The seventh house: This is the house opposite to your ascendant, the most difficult house to integrate, that's why relationship is hard for everyone because partner’s house is just opposite to yourself and you have to integrate opposite part in your life in the form of partner, without integrating opposite to you, you are not complete. The house is known as relationship and actual partner( spouse) house. What kind of partner you will get or you marry is seen by the 7th house. Your relationship will be influenced by Planets in the seventh house and depending on that they bring, as a natural indicator, as a house ruler, will modify your 7th house.
3. The seventh house ruler: Depending on what sign falls on 7th house, we look for where is its lord placed, In which sign, house and whether 7th lord conjunction or aspected by other planets. Based on whichever sign falls Often where the seventh house ruler lands shows the nature of the partner more than anything else.
4. Divisional chart for relationship ( Navamsa chart - D-9): For more detail about your partner and relationship in life, D-9 harmonic chart is very important in vedic astrology.
5. Moon: Moon is the capacity to receive. How you relate with others and how you act in relationship emotionally can be asses by condition of Moon.