Originally Posted by Rascal
AFAIK, he did not lose his titles (I believe they are of Nassau).
You are right, he did not lose his titles but if I'm not mistaken he renounced his rights to the throne upon marrying Joan who became a Princess of Luxembourg, Charlotte and Robert were born HRH Princess and Prince of Luxembourg. As Stefan already mentioned Julie and their three children became HRH Princes/Princesses of Nassau in 2004. AFAIK the children were raised in Luxembourg and France.
After Charles' death she married Philippe de Noailles, Duc de Mouchy, Prince-Duc de Poix who then worked as managing director of the Domaine Clarence Dillon; together the two bought Chateau La Mission Haut-Brion, Château Laville Haut-Brion and Château La Tour Haut-Brion. Robert now works as the manager and lives with his family in France while Charlotte is living in London with her family AFAIK.
Other information about Charles... He was a member of the Council of State for some time and served as President of the Board of Industrial Development. He attained the rank of Colonel of the Army. He succumbed to a heart attack at age 49 while at Villa Reale d'Imbarcati near Florence, Italy. He was laid to rest at the Cathedral Of Our Lady in Luxembourg.