NEW YORK — The elderly couple stabbed to death in their Brooklyn home had been trying to get mental health help for their son now charged with their murders, neighbors told the New York Daily News on Monday. Meyer Sperber, 48, has been charged with murder and weapon possession in the Saturday double killing on a typically quiet Borough Park block, police said Sunday. A neighbor who is a close friend of the family described the suspect’s escalating illness leading up to the slayings of the well-liked victims. Meyer Sperber’s mother planned on looking after him over the weekend. “The family want…