New York —- The Rockefeller family and shareholders pushing Exxon Mobil to focus more on renewable energy now have the backing of a powerful advisory group for institutional investors.

The RiskMetrics Group also came out in support of another proxy supported by the Rockefellers, who want the position of chief executive and chairman, currently held by Rex Tillerson, to be split.

The resolutions will be put to a vote May 28 at Exxon Mobil's annual meeting.

The group said it "believes that the separation of the roles of chairman and CEO would increase the independent oversight of management."

Peter O'Neill, a great-great grandson of John D. Rockefeller Sr., who founded the company that became Exxon, said last week that RiskMetrics' support "added considerable momentum" to the shareholder resolution.

The Rockefellers are trying to break the company free of what it considers a stodgy management structure that has failed to plan properly for changes in future energy markets.

Some family members said they are concerned that Exxon Mobil is too focused on short-term gains from soaring oil prices and should do more to invest in cleaner technology for the future. They argue that separating the leadership roles will better position the company to face future challenges.

Some shareholders, including some Rockefeller descendants, have launched a campaign to recruit support for their position. The group, called "Exxon For Owners," said it plans to meet with institutional investors and representatives of other proxy advisory firms to garner support for their initiatives over the next two weeks.

Exxon Mobil, now the world's largest publicly traded oil company, was formed by spinoffs of John D. Rockefeller's Standard Oil Trust.

It recently reported its first-quarter profit climbed 17 percent to $10.9 billion —- the second-biggest U.S. quarterly corporate profit ever.

Exxon shares fell 71 cents to close at $88.82 Friday after falling as low as $87.97 earlier in the session.