If a cohen has a relationship with a jewish woman who he is forbidden to have a relationship with, for example a divorcee, and they have a son, the son would not be considered a cohen, but does the father have to perform pidyon ha ben? Thank you very much in advance! I appreciate it very much! Yours sincerely, Ronald Wolf

Since, as you said the son's holiness as a cohen has been desecrated being born from a relationship forbidden to a cohen, and he is now a "chalal", he is not exempt from pidyon haben. The father therefore sets aside the amount but then keeps the amount for himself. (שולחן ערוך יור"ד שה:יט, ערוך השולחן: ס-סא) Should this be a practical question, please consult your local rabbi.