From Halopedia, the Halo wiki
Ellen Marcus is the wife of Sam Marcus, a technical officer who served under Captain Jacob Keyes on the UNSC Pillar of Autumn in September 2552. The couple had children with whom she lived on Earth. Due to the Covenant threat and Sam's call to duty, Ellen and her husband had not seen each other for over three years. Before his death, Sam carried a picture of her with him wherever he went.
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