Anthony Lane at The New Yorker:
Arbus inherited both strains: the urge to follow your star, plus the rage to cut yourself off and plunge into personal lockdown. One further twist in her upbringing was that she did not endure it alone, for her brother, Howard, was close to her, although whether that closeness offered aggravation or relief is open to debate. Both were precocious students, and they shared other talents, too. Diane masturbated in the bathroom with the blinds up, to insure that people across the street could watch her, and as an adult she sat next to the patrons of porno cinemas, in the dark, and gave them a helping hand. (This charitable deed was observed by a friend, Buck Henry, the screenwriter of “The Graduate.”) Not to be outdone in these vigorous stakes was her brother, who later, in a book called “Journal of the Fictive Life,” defined his self-abuse as “worship.” He added, “My father once caught me at it, and said he would kill me if it ever happened again.” A friend of Gertrude’s once told Howard that reading Freud would make you sick. On the contrary, it would be like a day in the life of the Nemerovs.
The summit of this weirdness comes before Lubow has reached page twenty, with the disclosure, from Arbus, that “the sexual relationship with Howard that began in adolescence had never ended. She said that she last went to bed with him when he visited New York in July 1971. That was only a couple of weeks before her death.” The source for this is a psychiatrist named Helen Boigon, who treated Arbus in the last two years of her life, and who was interviewed—though not named—by Patricia Bosworth for her 1984 biography of Arbus.