A friend of mine is in a relationship heading for marriage, he used to have a girlfriend whom he loved so much, but the girl dumped him for another London-based guy and migrated to UK. Now, after two years the girl got married abroad, his ex senior sister got a job in a bank where my friend works and to cut the story short both of them are now planning marriage. I am feeling like how is it gonna work but they dont give a damn. If you were my friend, can you marry your ex senior sister?