I've read all of the comments that were posted. Thank you so much for those who commented. I decided that  I would just play off ss's question like their not important.

Ss8-whose the woman in the bedroom?

Me- Why do you ask?

Ss8-When you and dad get married, are you going to be dad's husband

Me- Yup

stuff like that. 

Ss8 wouldn't leave fiancé alone when it was bed time, but he held his ground, tucked him in and said good night, then I tucked him in ;) 

I did listen to a conversation that ss10 and ss8 were having before I went into the kitchen to make them breakfast.

Ss8: it's weird that dad and Collin are getting married

Ss10: why?

S8: They're both boys (Bm words)

Ss10: Dad and Collin love eachother. Who cares?. Besides Collin loves us too and his way nicer than mom 

Ss8: no response.

Me: Who wants pancankes!.

Then later that day my little buddy(ss10) and I were playing catch. 

Ss10: can I ask you something?

Me: Yeah of course. What's up?

Ss10: When you and dad get married ,are you going to be my stepdad?

Me: I sure am bud

Ss10; When you and dad get married, can I call you dad "C"?

Me: You can call me whatever you want.

I was grinning the whole time. I feel all warm and fuzzy right now. Fiancé and Bm alternate weeks and i'm actually missing my little buddy right now. I need a break from ss8, but I want ss10 back here. Can't wait for next week. I can't wait for next year either, fiancé will be Dh and ss10 will officially be my ss. It's just sad that bm is manipulating ss8,Doesn't she know she's doing more harm than good.