Incest is sexual intercourse between close relatives (1,2) that is either illegal in the jurisdiction where it takes place or socially taboo. The type of sexual activity and the nature of the relationship between people that constitutes a breach of law or social taboo vary with culture and jurisdiction. Father-daughter was the most commonest form of incest, its prevalence is difficult to assess due to secrecy and privacy (3,4). In Iraqi law incest is a Forensic case usually referred to Medico legal Institute to be investigated with a high degree of care as a disputed paternity due to sever , danger sequel of punishment may reach to perpetrator execution. Aim of this study is to focus the light and report one of the important incest cases referred to Medical-Legal Institute .DNA profiles of 15 autosomal Short Tandem Repeat and Amelogenin markers were investigated for the (Father and father, s cousin, Mother and son) in DNA Typing Department. This case was rebated according to the match of all genetic markers of DNA profile of the son with that of the putative father (Mother s Father ). We conclude that the father can not be excluded from being a biological father of son who has 8 homogenous out of 15 loci suggesting high kinship relatedness between his father & mother. The Liklihood ratio was 99.99 %.