1. As per Brihat Jataka, if 7th house in navamsa chart falls in sign of Sun, Mars, Mercury or Jupiter only one marriage to be there despite some planetary positions supporting more than one marriage in the same horoscope.
2. Jupiter joined by Mercury - gives only one marriage as per Jyotish Ratnakar.
3. Mars with Rahu in 7th house, will give only one marriage, though other problems or discords may be there in the life of the couple.
4. Lord of 7th and also that of 2nd house placed in their own signs or in sign of exaltion or in subha-Varga.
5. 7th lord with Venus and no malefic influence on 7th house or 7th lord.
6. Saturn aspecting Venus, though a malefic influence in play, yet in marriage matters, it does not support more than one marriage, as some believe so.
Note: These are on|y general indication and should not be taken as
very binding rules it appears.