Complex sentence: In 556, Chlothar sent Charibert and his next youngest brother Guntram against their younger brother Chramn, who was in revolt against his father and was hiding out on Black Mountain in the Limousin.
Split into simpler sentences: In 556, Chlothar sent Charibert and his next youngest brother Guntram against their younger brother Chramn. Chramn was hiding out on Black Mountain in the Limousin.