Carlotta Mathieu (b.1989)
[only child together of Countess Christina Douglas (1951-2010) & her second husband Arturo Mathieu (1943-2000)] got engaged to Nicholas Gaggero (b.1985) last year.
She has two older half-siblings Gustav (DOB unknown) and Emma Winberg (b.1980) born from her mother's first marriage to Carl Johan Winberg (b.1944); Emma is engaged to James Le Mesurier, Gustav is married to Anna Lundin and they have a son William (b.2015).
Both their grandparents' on mother's side, .Count Jakob Douglas & Countess Hedvig Douglas, nee Thielers died this year.
Source: Descendants of Grand Duke Ludwig I of Baden