Okk..i still need help?

ok im writing his book..rite? and im to young so i need help giving it a titl, alot of people have been giving me really good ones but i need more..... its about a boy and a girl who love each other and there going out with each other, without anyone knowing... his sisters and the girl are reall close, practically best friends, but then one of them starts getting suspicious and starts looking into it. please help and i'll love you forevr:)