Obama also congratulated Harry and Meghan on getting engaged previous year - with the couple recently spending the anniversary of their engagement apart - and wrote in a tweet: "Michelle and I are delighted to congratulate Prince Harry and Meghan Markle on their engagement".
Henry, who was a good friend of both Prince William and Harry, passed away in a vehicle accident 16 years ago in 2002.
According to Sunday Times royal correspondent Roya Nikkhah, both Harry and Markle were involved in the service, with Markle giving a reading of the poem "Our Deepest Fear" by Marianne Williamson and Harry sharing an appeal for the charity.
Prince Harry and Meghan at the Centenary of the Armistice Service last month.
The former first lady of the U.S. was in London recently, where she met with Duchess of Sussex, Meghan Markle. She reportedly jotted down notes on a pad during the discussion. "They don't really get on", a source told the Daily Mail.
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Speaking about their friendship on her former lifestyle blog The Tig, Meghan said she and the tennis ace bonded very quickly when playing a game of flag football, which is a variation of American football.
"She wants to be on hand to help Meghan and Harry with the baby".
Until now, the Sussexes have lived in Nottingham Cottage - a two-bedroom house in the grounds of Kensington Palace, where the Cambridges also live.
While the 37-year-old doesn't have any specific patronages yet, it's clear to see where her heart lies when it comes to causes she stands up for.
Earlier this week, Michelle said in an interview with Good Housekeeping that her advice to Meghan would be to "take some time and don't be in a hurry to do anything".
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Her sister-in-law, April Burton, said she last heard from Stefaniak around 8 p.m. last Tuesday. Burton, however, left November 27, a day before Stefaniak was scheduled to leave.