The grandmother of former US President Barack Obama, Sarah Onyango Obama died at the age of 99 on Monday in a hospital in Kisumu, Kenya.

The former president tweeted about his grandmother Monday morning saying she was quoted “affectionately known to many as “Mama Sarah” but known to us as “Dani” or Granny. We will miss her dearly, but we’ll celebrate with gratitude her long and remarkable life.”

Sarah – who was the third wife of Barack Obama’s paternal grandfather – was a Kenyan educator and philanthropist who promoted education for girls and orphans. She was honored by the United Nations with an award recognizing her work to support education in 2014.

In his memoir “Dreams from My Father”, former President Obama often referred to her as “Granny” and described meeting her during his 1988 trip to his father’s homeland of Kenya where their initial awkwardness and communication struggles eventually developed into a warm bond.

She attended his first inauguration as president in 2009. She is expected to be buried on Tuesday.