Marriages are normally performed in the 7th house major or sub period and also in Jupiter and Venus major or sub period. If both partner’s chart is having strong Venus and the 7th house is good, not afflicted then such partners will have long lasting married life. If, there is weak Venus, Jupiter and the 7th house lord is placed in odd house then complications are indicated.
The Sun aspect to the 7th house or placement of Sun in the 7th house may give divorce. Divorce may be even in Jupiter major or sub period. The basic logic is after one divorce the 2nd marriage will be immediately performed.
The 4th house Saturn transit and seven & half years Saturn transit can be harmful
for the marriage, if Saturn is bad and related to the 7th house.
Never predict only by one chart, check both partners natal chart. If, one has less happiness in the marriage, but other have great happiness then that marriage may last or prolong.
The divorce and separation is also depends on many other factors, so be careful when you are predicting this. An illiterate and fully dependant lady of ancient thoughts will manage her marriage even at the cost of torturing and humiliations, but a well educated and financially independent with modern outlook will not do so.
The philosophy of life and culture also affect at great level to reduce the probability of divorce even chart is not great. To support my statement I will quote the Indian society before 1947, in that time divorce was very rare, but in Europe and America divorce was common. Now with drastic changes in social pattern and lifestyle of people of both sexes, complications in married life is at rise. In India too divorce rate is increasing.
It will be interesting to note that an average American may marry more than twice sometime thrice in their life. Do you think all are having bad 7th house? No, it is not. Even the chart may be good, but the philosophy and thinking makes strong impact. Now people divorce even for a very silly reasons because for them life is too short to compromise. Whereas marriage is nothing but a compromise and everyone has to do.