Twentyseven-year-old John McDonald met Nanqueen Romero, 31, at an internet chat room and they talked online for weeks, before Romero invited him to visit her in Angono in the Philippines.
McDonald didn't have any clue that she was living-in with Anselmo Lacostales. She had introduced Lacostales as her brother, The Sun reported Tuesday.
He reached the Philippines Thursday and went to Romero's home near capital Manila Saturday.
"From what we understand, she introduced her live-in boyfriend Lacostales as her brother. But trouble came after they all went to dinner to a restaurant," a police spokesman was quoted as saying.
As soon as McDonald said that he plans to ask Romero to marry him, Lacostales lost his cool.
When they reached back at the house, Lacostales grabbed a knife and repeatedly stabbed McDonald and Romero.