The eldest son of a Long Island woman accused of stabbing her husband to death returned to the family’s home last night determined to support his devastated siblings.

“It’s the worst possible time,” Matthew Prisco, 22, said outside the Fort Salonga house where Kathleen Prisco allegedly stabbed pension and tax lawyer Ralph Prisco, 54, more than a dozen times with a kitchen knife on Friday.

“There will come a point when I can speak about my family and about who we are, but this is just very difficult right now,” said Matthew, who graduated from Princeton University in June.

Neighbors were shocked, but one woman said the normally reserved Kathleen, 48, had appeared particularly withdrawn in recent days. Matthew, who found his dad’s body, is handling the funeral arrangements as he watches over his sister, Melissa, 19, and brother, Christopher, 17.