NEW YORK — The “Madame Melville” opening on Thursday night at the Promenade Theatre was a family affair as mum Vanessa Redgrave flew in from London and sister Natasha Richardson walked a few blocks west from her CPW abode to catch Joely Richardson in her Gotham stage-acting debut.

The actress plays the older woman who deflowers a 15-year-old, Macauley Culkin, in Richard Nelson’s play. Was there a Madame Melville in the playwright’s youth? “In some way every play is autobiographical,” said Nelson, whose next stage project definitely is not: a new adaptation of Chekhov’s “The Seagull,” to star Meryl Streep and Kevin Kline under the direction of Mike Nichols in Central Park this summer.

Nelson nabbed the Chekhov commission last year, even though he doesn’t speak Russian. “The important thing is to translate intentions, not prose,” he offered.