Extra marital mainly caused by a planet and a type of signs. Planet is mercury and signs are dual signs, and yes also signs of Jupiter they are also dual. Jupiter’s/Brihaspati’s wife cheated him, tara devi. Now, she went to the Moon and had a child, named Budh/Mercury. Now, All 3 Mercury, Moon and Jupiter are important in extra marital affairs & Nakshtra & Signs of them as well.
Above written planets and Sign should have malefic influence of Mars, then Saturn can also be but Mars is the main trouble maker in this. Rahu-Ketu alone can’t do, especially Ketu. They should have the influence of Mars or Saturn and with Mercury or the Moon.
People say Rahu is the cause, mostly. But Rahu can even limit your relationships. He is an illusionary planet, giving illusion to astrologers as well. So don’t see Rahu as extra marital affairs always. He can be, if found in influence of the above written things.
Important Houses: Upchaya houses give multiplicity, 11th house is more important. 8th is secret affairs.
7th house is the main house of spouse and relationship, but also focus on ascendant because it is 7th from the 7th house, bhavat bhavam principle.
Now, the Lord of house is important. See if lord is found in such above association then person will do such things intentionally and if house is associated and lord is good, then he is not doing intentionally but his marriage broke for some reason and then he has to do a second or third marriage. Difference of house and lord is very important, I have explained this in one of my Youtube Videoshttps://youtu.be/4NE9XumDmmQ.
Secondarily, see the dhana yogas. You must have seen rich people have multiple marriages and affairs. Dhana yoga is very important with the above combinations. Dhana Yoga is formed by association of 2nd and 11th house/lord with trine houses/lords, 1st, 5th or 9th. See it in D-9 only.
Charts to be used: D-1 and D-9 are most important. If birth time is correct than see from D-60 too. If found from the Moon chart then the person will have only such thinking and not physically.
Jaimini Angle: Darakaraka and Upapada lagna should also be seen for 100% confirmation. They can be in association with the above dual planets and signs.
Note: Jaimini astrology is not different from Parashar, both are described by a sage Parashara ji, though Jaimini Rishi has done more work on it.
Apply all above things and then deduce any results, it will give you 99.99% results. Please don’t go in snapshots techniques, it may lead to failure.