The sisters were originally seeded eighth and 24th but their positions were revised following the withdrawal of second seed Kim Clijsters.
Serena was top of the WTA rankings when she won her fourth Wimbledon singles title last year, her 13th major singles crown in all, but is now down at 26 after 11 months out through injury and serious health problems.
The 29-year-old American required surgery on her foot after slicing it open on broken glass in a Munich restaurant last July and then needed emergency treatment in February for potentially life threatening blood clots on her lungs.
She returned to action this week at Eastbourne after taking a wildcard.
Venus, who has won five Wimbledon singles titles but is now ranked 33, also made a comeback in Eastbourne after not playing since the Australian Open because of abdominal and hip injuries.
The sisters, who between them have won nine of the last 11 singles titles at Wimbledon, have been upgraded at the discretion of the All England Club to ensure “a balanced draw.”
The rest of the seedings follow the WTA rankings with Denmark's world number one Caroline Wozniacki topping the draw. The men's seedings, based mainly on the ATP rankings on June 13 but which can be tweaked to reflect grasscourt form, have a top four of defending champion Rafael Nadal, Novak Djokovic, six-times champion Roger Federer and Andy Murray.
American Andy Roddick, three times a runner-up, has earned the eighth seeding spot despite a current ranking of 10. Frenchman Jo-Wilfried Tsonga has also been shunted up to 12th from a ranking of 19 after his run to the Queen's Club final.
Sania-Elena seeded fourth
India’s Sania Mirza and her Russian partner Elena Vesnina are seeded fourth in the women’s doubles. Sania and Vesnina, who joined forces earlier this year, reached the final of the French Open this month.
In the men’s doubles, India’s multiple Grand Slam winners Leander Paes and Mahesh Bhupathi are seeded third.
Rohan Bopanna and Pakistan’s Aisam-Ul-Haq Qureshi, who won their second ATP title together at Halle last week, are seeded fourth.
