Peter Joseph Kovacs was the former husband of Sylvia Kovacs.
Their marriage became strained in the late '30s, and each of them accused the other of psychological abuse and adulterous affairs. The two divorced, and presumably never met again.
For the following 3 years, Sylvia changed between low-cost apartments, sometimes with male companions. Peter is not the biological father of Walter Kovacs (aka Rorschach), as he and Sylvia were divorced years before Walter's conception.