YES THEY CAN BE BUT IF YOU THINK YOU WANT TO TRY DON'T EVER TRY IT THAT WILL RUIN YOUR LIFE IN LONG TERM ONLY EXCEPT YOU WANT TO MARRY HER IN FUTURE. I HAVE SEEN ONE COUPLE WHO TRIED TO PROVE THEMSELF AS BEST FRIENDS EVER SINCE THEIR COLLEGE LIFE. WE ASKED HIM TO BE IN DISTANT WITH THAT GIRL AND HE SAID NO ITS JUST A FRIEND SHIP AND WE NEVER GONNA DO ANYTHING WRONG AND HE SAID HE GONNA PROVE WHAT THE REAL FRIENDSHIP IS OTHER THAN MARRIAGE. HAHAH..... AFTER FEW YEARS THEY SCREWED UP EACH OTHER. WHEN THEY STARTED COMBINED STUDY DURING FINAL TEST ....... GONE WILD AND NOW THE GUY IS LIVIGN WITH HIS WIFE AND " RAKHAUTE( SO CALLED TRUE FRIEND)"  NOW HIS WIFE LIVES WITH FAMILY IN HOME AND HIS " RAKHAUTE " WIFE SO CALLED TRUE FRIEND IN RENTED HOUSE.

AND NO WONDER NOW THEY HAVE BABY ALSO.... SO .... WHAT GREATER EXAMPLE I CAN GIVE YOU MORE THAT THIS FOR FRIENDSHIP OF BOY AND GIRL.