Mrs Olivia Emilie DEAN, née Jkvr Olivia van VREDENBURCH (born 17 IV 1991), is indeed a daughter of Jhr Hugo Henri Carel van VREDENBURCH (born 9 XII 1965) and his wife (marriage registered Q1 1990 - North East Hampshire), Natasha Lilian ("Sasha") BURTON (birth registered Q1 1967 - Chichester). She and her twin sister, Jkvr Tatiana Julia van VREDENBURCH (see here for Netty Leistra's posting about her engagement in 2020 -
https://groups.google.com/g/peerage-news/c/wase6ooPO4Q/m/yoDZZpqWAQAJ) were born in Tokyo, Japan.
Sasha van Vredenburch, née Burton, is the second child, and eldest daughter, of John Donne BURTON (born 3 II 1932) and his wife (marriage registered Q3 1963 - Chelsea), Olivia J GUBBINS. Her next sister, Miranda Lisa BURTON (birth registered Q1 1969 - Petersfield), is the wife of David William Samuel MONTAGU (born 21 I 1970), a grandson of the 3rd Baron Swaythling (N.B. David Montagu's elder brother is the heir presumptive to their cousin, the present 5th Baron).
Jhr Hugo van Vredenburch is the eldest son of Jhr Carel Lodewijk Hendrik van VREDENBURCH (22 II 1932 - 14 XI 2023) and his wife (married 19 X 1963, divorced 1991), Jkvr Julie Christine QUARLES van UFFORD (4 I 1944 - 7 II 2007), a daughter of Jhr Pieter QUARLES van UFFORD (24 XII 1914 - 17 IX 1999) and his wife, Wilhelmina Johanna Ada TAMELING (1917 - ?), who were also the parents of Jkvr Emilie Elise Christine QUARLES van UFFORD (born 19 III 1946), who was the wife (married 10 VI 1971) of Hugh Bernard Edward van CUTSEM (21 VII 1941 - 2 IX 2013), of that landed gentry family.
Jhr Hugo van Vredenburch's youngest brother, Jhr Ernest Ewoud van VREDENBURCH (born 24 VIII 1969) and his wife, Lucy Jane HART (born 2 VII 1969), have a son and three daughters: Jhr Hugo Willem H J (birth registered March 2003 - Colchester), Jkvr Isabella Florence Elise (born 4 VII 1996) and twins, Jkvr Eliza Poppy Jane and Jkvr Saskia Christine Daisy (births registered April 1998 - Westminster).