His father, Friedrich, Count zu Leiningen-Westerburg (1761–1839), inherited the county of Altleiningen, but had divorced his first wife, Charlotte von Zech und Rautenburg (1777–1841), in 1798 after six years of childless marriage.
By the time Count Friedrich remarried Eleonore Maria Magdalena Breitwieser (1781–1841) in 1813 (initially morganatically, whereupon she became created Frau von Brettwitz) he already had several children by her, legitimised by their parents' marriage.
In the autumn of 1848, the Temesvár regiment was mobilized, and Károly volunteered for the campaign waged against the Serbs.
His last recorded words were: "I have only just learned the tidings blared by the newspapers...I have no documents with which to refute any incident, but I have faith that at the last God's skies will open before all -- and when I come before the throne of God's eternal judgment -- these allegations of me shall be solemnly denounced as low slander."
In 1999 a bilingual memorial tablet was erected at his birthplace in the monastery/castle in Niddatal-Ilbenstadt by the Association of Hungarian Organizations in Germany (Bund Ungarischer Organisationen in Deutschland e.V.