Family Graph?

[text] Cycles in family tree software a 1425 v x 389 1 am the developer of some family tree software written in C and Qt. had no problems until one of my customers mailed me a bug report. The problem is that he has two children with his own daughter and as a result he cant use my software because of errors. Those errors are the result of my various assertions and invariants about the family graph being processed for example after walking a cycle the program states that X cant be both father and grandfather of Y How can resolve those errors without removing all data assertions c graph cycle assertons familyree