Jennifer Lopez and Marc Anthony's Separation has taken a back seat.

Nearly a month After the couple split, the two singers were spotted basking in the Long Island sun near Sagg Main Beach in Southampton ... inside a red Mustang convertible


No explanation yet for the unexpected reunion today -- but Marc's rep tells TMZ, he was on the East Coast visiting his children.

Marc has sired five offspring in total -- one out of wedlock, two With his first wife, and two With Jennifer. It's unclear which children he was visiting

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