Life lessons?

In life have you ever heard the phrase "Blood is thicker than water"? I have and im sure everyone else has too. This is in reference to the bonds in family are to run deep, in relation to the friendships between random people. At what point do you decide when you blood throws your bonds aside to reciprocate the action and isolate them from your life? Moving on.. The reason that could seperate two cousins that were closer than brothers... a classic... a girl or as may be a pair of girls. My ex and his girlfriend had become good friends so as it would be when the shit hits the fan women side together. This is to be expected and is not overly suprising. Now im not sure if you can see where this is going yet but stay in the car were getting there. Now when the slander hit the gossip stream and everyone was throwing me under the bus I would have felt that my cousin would have had my back. This was not the case. Maybe I need to look at it from his side that if you still want to get laid you need to play ball... That aside I felt that if you can throw aside years of bond and blood relation then it is what it is. This bring it back to the origional question. Maybe Im just holding a grudge and I am the problem. Im not sure what to say but a cousin that I have almost been brothers with for 25 years, I have almost not spoke to in atleast a month with no signs of improvement. Im not sure what to think.