To me that is not strange. My cousin's ex just recently unfriended me on FB. My cousin sent a note out on facebook (to everyone) that her ex would be unfriending a lot of her family, and they are also unfriending each other on FB. It probably comes to a point where it becomes awkward if you remain friends on FB.
If my H and I were to separate, I would de-friend him and probably a lot of his family, as it would be too difficult for me to keep get updates on his new life. It would not be personal, or anything against them, but for my own reasons. I love my H's family and I am actually sad that I might lose the connection that I currently have with them.
I would not worry about it too much hotwheelsaust.
M: 8 yrs T:14 Twins:7 S:5 BD:'NLILWY': Feb/2013 Mar/Apr/May: MC June: "living in limbo" Sept 12: H moves out Oct 20: reconciling Jan-Feb 2014:MC Feb 2014: separating, and H moved out.