Jeff decided to turn his sister into a sexy parasite suit. He selected her then selected to turn her into a parasite suit. Jeff clicked through the options for the parasite suit and found some interesting. He then made his choices of what abilities his sister will have as a parasite suit.
He made it so she can only attach to one host, said host will be their neighbor Gabriel. He made it so his sister will slowly turn Gabriel into the woman she (his sister) wants/dreams to be, after which she will drive Gabriel mad with lust and fuck and impregnate the transformed Gabriel.
Jeff then made it so Gabriel would live with them so he could watch his transformation. Jeff hit enter and watched as his sister change on the screen into a sexy parasite suit and attach herself to Gabriel.