You have been misled by the few astrologers. There is no such axiom in Astrology. There are too many wayside astrologers who are not properly educated and behave as experts in Astrology. Read my blog navagrahastro.blogspot.in which will give you a better insight into the scope of astrology.
When kethu is in first house,it means that rahu is in
seventh house. It is a negative point for happy married
But that single point will not decide your entire married
You have to see which planets are seeing seventh house,
where seventh lord is placed and how Sukra is placed. email@example.com