Williams was not originally expected to enter the event but lost in the first round in both singles and doubles, teaming with sister Serena.
As expected, the biggest-name team announced Tuesday was 14-time major champion Rafael Nadal paired with French Open winner Garbine Muguruza. The Spaniards are seeded third.
The most anticipated team before the Olympics — Switzerland's Martina Hingis and Roger Federer — didn't happen when Federer withdrew because of a knee injury.
Another top women's player who lost in the first round, Agnieszka Radwanska, will also get an additional shot at an Olympic run. She'll play with Lukasz Kubot for Poland.
The top two seeded teams are from France: Caroline Garcia-Nicolas Mahut and Kristina Mladenovic-Pierre-Hugues Herbert. Mahut and Herbert were seeded No. 1 in men's doubles but lost in the first round.
Mladenovic and Herbert face Italy's Roberta Vinci and Fabio Fognini in the opening round. Fourth-seeded Sania Mirza and Rohan Bopanna of India meet Australia's Sam Stosur and John Peers.
Other notable pairings in the 16-team field are Spain's Carla Suarez Navarro and David Ferrer, Britain's Johanna Konta and Jamie Murray, and Bethanie Mattek-Sands and Jack Sock of the United States.
The 32-year-old Ram is coming off a semifinal appearance at Wimbledon in men's doubles.
Mixed doubles play begins Wednesday.