Marian Robinson, the mother of former US first lady Michelle Obama, who moved into the White House with the first family, helping care for her young granddaughters and providing a stabilising presence in one of the world's most stressful residences, died on Friday, her family said.

"We needed her. The girls needed her. And she ended up being our rock through it all," her family said in a statement. Robinson was 86.

Though she eschewed the spotlight, Robinson was present for some of the Obama family's most visible moments, often appearing at holiday celebrations or other events alongside the first couple and their two daughters, Sasha and Malia.

On election night in 2008, she was famously photographed holding her son-in-law Barack Obama's hand while the two sat on a couch as results poured in, sweeping him into office as the nation's first Black president.

"At every step, as our families went down paths none of us could have predicted, she remained our refuge from the storm, keeping our feet on solid ground," the statement read.

Robinson was born in 1937 and grew up on the South Side of Chicago, one of seven children, before studying to become a teacher and working as a secretary.

She married her husband, Fraser Robinson, in 1960, and the couple had two children, Michelle Obama and her brother Craig Robinson, both of whom were also raised on the South Side.

Fraser Robinson died in 1991 after a long battle with multiple sclerosis.

"The trappings and glamour of the White House were never a great fit for Marian Robinson," the statement from her family said.

Rather than socialising with White House VIP guests, she preferred to spend her time upstairs with a TV tray, in a room near her bedroom with enormous windows overlooking the Washington Monument, the statement said.

She enjoyed sneaking out of the White House to run errands, such as popping to the drug store.

In the Obamas' eight years at the White House from 2009 to 2017, "the only guest she made a point of asking to meet was the Pope," her family said.

Robinson is survived by both her children, their spouses and six grandchildren.

"She passed peacefully this morning, and right now, none of us are quite sure how exactly we'll move on without her," the statement said.

Agence France-Presse