Will be there NTR or incest? (I hope YES but in separate ways)
NTR? Depends on how you define NTR, all the girls work in a sex club and have sex with other people if you are talking about people stealing your girl.. then no.
Incest? The MC isn't related to anyone, so... no. There are a few scenes where the MC takes both sisters at once, but the sisters don't interact with each other.
But if you want, I'm sure Manny is up for being your Mommy...
Sandra could also go for some sister role-play.