Stellar Astrology (Nadi Astrology) is a predictive system of astrology which gives importance to houses, constellation & sub lord signified by a planet depending upon its degree in the astrological chart. In this system, a planet gives results not on the basis of its natural significations or the houses it owns but on the combination of houses signified by the planet, its constellation lord & the sub lord. A single house is not capable of giving any result & it is very difficult to assess results of a planet without looking at its constellation lord & sub lord. For eg: Second house signifies a number of things but we cannot pinpoint anything unless we see the other houses that the planet is signified through itself, star lord or sub lord. If the planet is also signifying the eleventh house, then either it can mean "Gain/Addition of a member in the family" or "Gain of money & assets" - those who follow astrology knows the second house
Mangal Dosha is an astrological combination that happens when a person has Mars (Mangal) in the 1st, 2nd, 4th, 7th, 8th or the 12th house of the Birth Chart. Person born with such planetary alignment is called a Manglik . It is believed that it is a bad placement and if a Manglik marries with a Non-Manglik then the fiery nature of Mars (Mangal) will bring trouble, tension, problems in the marriage and may eventually lead to the death of the later one. A Manglik should only marry with another Manglik in order to cancel out the negative effects of this placement and to enjoy a happy married life.