Keith Sébastien Knecht de Massy, or Sébastien as he is known by the family, was born the son of Christine Alix de Massy and Charles Wayne Knecht on 24 August 1971, in Philadelphia, PA. In addition to being a 1st cousin once removed of the present reining Monégasque Princely Family, he is also a distant cousin of the family on their maternal side as his father was a cousin of Princess Grace (I believe Sébastien's grandfather was Princess Grace's uncle on her father's side).
He is a member of his aunt Baroness Elisabeth-Anne de Massy’s organization, All-sports Country team (A.S.Co.T., Team Monaco captain) of the tennis tournament. He also serves as founder and director of the board to his wife's organization, ConservationGuardians.
After obtaining his BA in business, Sébastien moved to Lima, Peru to work for Grana y Montero Petrolera. After living in Peru he moved back to Monaco and started his shipping career with the V. Ships Group. This brought him to live in London, Singapore and Paris. In 2005, Sébastien founded Madison Marine and today controls a fleet of merchant vessels.
In 2008 he co-founded Transport & Commodities which is based in Monaco and manages shipping, upstream and mining ventures.
He is a citizen of Monaco, where he resided with his wife Donatella, and four daughters until 2011 or 2012, now the family resides in South Africa. His daughters are:
he attended his mother's cousin's wedding ceremonies with his wife and three elder daughters. He also attended the Eagles and JM Jarre concerts (sitting in front of Princess Charlene). That November, he and his wife appeared with the family during the National Day festivities, at the church service, during the honor guard ceremony ( behind his wife, who is across and behind Princess Stephanie) and of course, on the balcony. In 2015, he and his wife were present during the baptism of the Princely Twins and his whole family was present for Prince Albert II's 10 year celebrations (Sébastien can be seen dead center, the really tall guy, his two daughters Christine and Andrea can be seen in front of him next to Charlotte Casiraghi, and his 3rd daughter Alexia is to his right between Charlotte and Pierre. I also think that his wife Donatella is directly behind-thus hidden behind-Charlotte.).
He shares a birthday with the son of his maternal first cousin 1x removed, the elder son of Prince Albert of Monaco, Alexandre Coste Grimaldi.