1968 New Haven Connecticut

I am looking for my brother's biological siblings. He was born February 20, 1968 in either New Haven or Hartford Connecticut. His birth name was Mark Joseph (don't know the last name). In June, at the age of 4 months, he was hospitalized with Spinal Meningitis. We are not looking to disrupt anyone's life, but would like just to know. We have heard many stories about his birth, including one that says his siblings were told he died at birth. Other than that, we were told he was primarily raised by his sister and his parents were elderly. An old baby book lists the names Wendy, Barry, Lisa, and Sandy, but we do not know if these are siblings or not. Any information would be appreciated.