According to texts, the sixth, eighth and twelfth houses from Lagna are considered to be unfavorable and among them, the eighth house indicates death, losses, adversity, misery, misfortune, separation etc., Scholars opine that the eighth house from Lagna or the Moon should not be tenanted as all planets irrespective of their being benefic or malefic produce evil in one way or other when in this dustana. It is a general rule that the bride horoscope would have the eighth house free from the occupation of any planets.
Sun in the 8th house may cause widowhood or severe calamity to the husband whereby the native will be drowned in sorrow. Moon in the 8th house may make one cruel, ugly, ill-dressed, angry and even aggrieved and if the Moon is weak, he may make her a widow or cause severe adversity to the husband and even otherwise she may not have conjugal happiness. Mars in the 8th house indicates that the native might be a prostitute and if such Mars is in conjunction with a malefic, the native will have no husband or she will become a widow or reject her husband and accept a paramour. If Mars in the 8th house in the horoscope of a male is likely to cause his own death.
Mars in the 8th in the natal chart of a female will cause her husband's death. Thus there is Kuja dosha in both cases. Mercury in the 8th house may make the native commit sinful acts, be cruel and unrighteous and she may become a widow or be a grief-stricken on account of severe mishap to the husband if Mercury gets afflicted. Jupiter in the 8th house denotes loss of children.
The native may have abortions or the children may die early if Guru is in the 8th in his own house. If Guru is in the 8th house is with Kuja, the pregnancy may end in miscarriage. Sukra in the 8th house makes the native haughty, aggrieved but resourceful, cruel, cheating in nature, ill-dressed and unrighteous. If Sukra is weak, the natives is likely to become a widow and more so, if in conjunction with Kuja. In any case, she will be quite unhappy with regard to her married life. Sani in the 8th house may make the native a widow especially if aspected by Kuja, sinful, cruel, unrighteous, dishonest and cheating in nature and her husband will always be sick or her married life will be with no romance and charmless. Rahu in the 8th house is said to be a Vishakanaya or one who violates the tradition of her family and becomes a widow. If the week moon is also in the 8th house with Rahu, widowhood is almost certain. If this combination of Rahu, Chandra has the aspect of Kuja, the native may become a widow in her 18th or 36th year. Ketu in the eighth house is likely to make the native a widow in life, probably during the Dasa of Ketu is not associated or aspected by a strong malefic.
Before proceeding for marriage alliance, it is advised the readers to take into consideration of the 8th house and its aspects on and take a professional astrologer's guidance. Mere matching of stars is not sufficient and in-depth analysis is advised for a happy life. During my three decades of experience, we found that the success rate is more than 80 to 90 percent after careful analysis of the natal charts of both the boy as well as girl.