The second and fourth houses represent family and domestic happiness and peace. The twelfth house is related to the pleasure of sleeping. The first house shows the nature, personality, personal qualities and behavior of the person towards others. Whenever the above mentioned malefic planets sit in these houses related to marriage in a horoscope, then the person is called Manglik. According to astrology, a Manglik person should not be married to a non-Manglik person because doing so can cause trouble in married life.