If Mangal (Mars) is present either in XII, I, IV, VII or VIII house of the birth chart or lagna kundali of a person then the birth chart is said to contain Manglik Dosha or the person is called manglik or mangleek in Jyotisha of Pandits. So called astrologers say that a manglik man should get married only to a manglik woman or vice versa otherwise problems may arise in married life but practically a lot of exceptions are observed in this rule of so called astrologers. Even many married couples are seen in which the one person is Manglik & the other one is non-manglik & they are enjoying a happy married life from decades. Such a Dosha is not a part of Indian Vedic Astrology & is a deep rooted superstition in Indian society.
Married life can only be determind by the seventh house or the house of marriage as well as the condition of Guru or Brihaspati or Jupiter in the birth chart. For men, the condition of Shukra or Venus also plays a pivotal role. Similarly for women, the condition of Mangal or Mars also plays a pivotal role. Time phase according to mahadasha-antardasha of grihas also plays a crucial role.