Hey, writers - there are lots of better ways for Liam to find out that his father and wife had sex together!
Leaving all the doors open with Bill and Steffy talking as loud as they can about it, is just not too believable to me as a viewer. Who does that? No one. But then most families don't interchange all the family members as sex partners either.
There are so many different ways to write a story about Liam finding out. Stop taking the easy way out; make it interesting.
Ha-Ha Ha-Ha.....It will be the first thing mentioned,quite loudly, every time Steffy and Bill meet for the next several weeks...errr months!! They maybe will bring it up a couple time more during a conversaion, just in case someone had not heard them when they took a sip of drink, during the middle of the bill/Steffy repeat!