Answer
Queen Fabiola and King Albert II were indeed related by marriage. King Albert II, who reigned as the King of Belgium from 1993 until his abdication in 2013, was married to Queen Fabiola from 1960 until her passing in 2014. Queen Fabiola was the daughter of Don Gonzalo de Mora y Fernández, 1st Marquis of Casa Riera and a distant cousin of King Albert's mother, Princess Paola.