Okay so they'd be 7 years apart! That works because Enslie would have been out of the house (I'm guessing) by the time their mom slept with Spencer's boyfriend. With the age gap I can see Spencer going to her a lot for advice and someone to talk to. I'm sure when she caught her Mom she called Enslie sobbing and freaking out. I think I'm going to make it when she was 17 and her boyfriend 18.