Re: cousin marriages......
Does this boy actually know that he's actually a BACK UP, or does he think he is formally betrothed to u?
If u r actually engaged to eachother, its not fair or right to check out other people. As u r young and will b in a position to meet other eligibles, u shold let him know this. For example, u could say,
"Dear cousin, i feel i am too young to decide if i want to marry you, so u should know that i may b looking at others whilst bearing u in mind as a potential partner. It is only fair that u do the same. Aaghe kismat ke baat hai."