Kim Kardashian joins sisters Kourtney and Khloe in the Hamptons

The extended Kardashian family continued their time in the Hamptons Monday as Kim Kardashian joined her sisters for lunch and took in an exercise class.

The family weekend began Thursday for the Kardashians, who celebrated Khloe's 30th birthday aboard a yacht in Manhattan. The sisters and mother Kris Jenner, 58, then headed out East, where the upcoming E! reality-TV show "Kourtney & Khloe Take the Hamptons" is being filmed.

Us Weekly said that Kim Kardashian, 33, and eldest sibling Kourtney, 35, had lunch around midday yesterday at the upscale restaurant 75 Main in Southampton. The magazine said Kim Kardashian wore a black tank bodysuit with a pleated black and white skirt with a green waistband, while Kourtney Kardashian -- who told her longtime boyfriend, Eastport-born Scott Disick, 31, that she was pregnant in a preview of this season of "Keeping Up with The Kardashians" -- sported a blouse with white-on-white vertical stripes tucked into high-waisted, pastel-colored striped shorts.

The magazine added that at some unspecified time the two and youngest sister Khloe Kardashian worked out at celebrity trainer Tracy Anderson's studio in Water Mill.

The new E! series, produced by the same companies as the flagship show "Keeping Up With The Kardashians," focuses on Kourtney and Khloe Kardashian as they attempt to relocate their Dash boutique from Spring Street in Manhattan's SoHo to a location elsewhere while also trying to open a separate pop-up store -- their first -- in the Hamptons.