I am playing a game right now as Eastern Rome I.E. The Byzantine Empire and I have gone through 3 generations of my family tree...see picture below.


And my question is about the France relations trait, The first marriage was to the Kingdom of Jerusalem and the second one was to the Kingdom of France, now the question is if I keep the bloodline pure such as only marrying my faction heir which stays on the left side of my faily tree will I get a bonus for the children created from that line. Example: I'm France and I only marry into the Holy Roman Empire family. Makes sense??