Hm, not so much a 'bug' as an unusual edge case that the scripts aren't built to recognize.
Basically, if someone who's in a relationship, but not with you, has your child...the script for 'you cucked someone' runs. There's not an easy way to make a script recognize the specific history of a complex and unusual situation like you're describing.
You could alter the dialogue/narrative of the 'you cucked someone' script though, so it didn't make the assumption as openly. I've been tweaking some of the scripts along similar lines, since the existing writing can be a bit offputting sometimes.
Basically, if someone who's in a relationship, but not with you, has your child...the script for 'you cucked someone' runs. There's not an easy way to make a script recognize the specific history of a complex and unusual situation like you're describing.
You could alter the dialogue/narrative of the 'you cucked someone' script though, so it didn't make the assumption as openly. I've been tweaking some of the scripts along similar lines, since the existing writing can be a bit offputting sometimes.