WASHINGTON — Former First Lady Michelle Obama’s mother, Marian Robinson, has died, according to a family statement shared with NBC News. Robinson was 86 years old. “She passed peacefully this morning, and right now, none of us are quite sure how exactly we’ll move on without her,” the family statement said. The family statement is from Michelle and Barack Obama; Craig Robinson and his wife, Kelly; and Marian Robinson’s grandchildren, Avery, Leslie, Malia, Sasha, Austin and Aaron. Robinson became known to Americans as the country’s first grandmother after her son-in-law, Barack Obama, won the 2008 presidential election. She was a…