I accidentally dragged my mom character onto her 18 year old son and the two proceeded to make a baby!

He registers as being "legitimate" but I know the truth!
Please tell me this is something that shouldn't be happening! I know with the VV games, you couldn't always get around it, but this is just one family at a time and it's just too much for a simple game like this. What's worse is that the wife kept refusing the husbands advances and then on the one slip-up, she goes and accepts her son. Ayayay!