Count Carl of Castell-Castell, initiator, vice president, and business manager of the Adelsverein, the son of Count Albrecht Frederick Carl zu Castell Remlingen and Sophie Amalie Charlotte (née Countess of Löwenstein-Wertheim), was born at Castell, Lower Franconia, near Würzburg, Germany, on December 8, 1801. He was descended from a long line of Franconian knights and nobles dating back to the thirteenth century. After receiving his basic education at the private school of Castell and military training in the royal Bavarian cadet corps, Castell entered military service in 1819 with the rank of cornet in a royal Hanoverian hussar regiment. In 1833, after having attained the rank of major, he left Hanoverian service. The same year he entered the Austrian army, and for the next several years he served in Moravia, Hungary, Dalmatia, and Vienna. In 1841 he was appointed to the post of governmental adjutant, with the rank of captain, at the Austrian garrison in Mainz. Inspired by books that he had read about Texas and by the Texans' struggle for independence, in 1842 he organized a society in Mainz for the purpose of directing German emigration to Texas. On April 20, 1842, when twenty-one noblemen met at Biebrich-on-the-Rhein, near Mainz, to form the association later called the Adelsverein, Count Carl of Castell was elected vice president and business manager of the organization. Under his management the society was reorganized in March 1844 into a stock company, and eight months later the society's first shipload of immigrants disembarked at Port Lavaca, Texas. Castell served the society as business manager and vice president until 1847, when the conduct of the society's business was placed in the hands of a committee. In 1848 he returned to his post as business manager but remained only until the society was reorganized that same year under new leadership. Count Carl of Castell led the society through its formative years as well as during the financial difficulties in the mid-1840s of settling immigrants on the Fisher-Miller Land Grant. He had an intense personal interest in the success of the colonization venture but little business acumen. The failure of the society was due in part to Castell's own blunders and omissions. In the latter years of his administration, in desperate attempts to save the reputation of the society and the investments of its stockholders, he even practiced deception and intrigue.
In 1846 Count Carl of Castell succeeded Count Ludwig Joseph von Boos-Waldeck as aide-de-camp to Duke Adolf of Nassau, the protector of the society, and early in 1850 he was promoted by the duke to the rank of colonel and appointed chief director of the war department in the Nassau Ministry of State. A few weeks later, however, on March 2, 1850, Castell succumbed to a fatal liver disorder. Among the several settlements founded in the 1840s by the Adelsverein, one was named Castell in honor of the count. The community was originally on the north bank of the Llano River but now is on the south bank in the western part of Llano County near the Mason County line.