We report an unusual case of a familial complex chromosome rearrangement (CCR), ascertained through prenatal diagnosis. The fetus carried an apparently balanced CCR with a recombinant 3-segment chromosome derived from two paternal reciprocal translocations involving both homologs of chromosome 14 and chromosomes 15 and 21, respectively. A probably normal phenotype was predicted and confirmed after birth. His older sister carried an unbalanced karyotype with partial trisomy 14 and partial monosomy 21, and displayed an apparently normal, paternally derived chromosome 14 that resulted from recombination between two derivative chromosomes. Fluorescent in situ hybridization (FISH) and molecular studies were essential for the characterization of the rearrangement. The "rebuilding," through recombination, of a chromosome involved in two different translocations in a progenitor, was demonstrated for the first time by molecular analysis. Our family is another good example of how balanced familial complex translocations are in a state of flux and can change from one generation to the next.