Get him to cum outside

You can't allow Rowol to cum inside his sister. She's only 18. She's too young to be a mother.
You use your mind trick on your son and say, “You will pull out.”
Rowol suddenly stops his thrusting and says, “I will pull out.”
Immediately after, Rowol does indeed pull his dick out of his sister. Then he holds it above her belly while he masturbates until eventually he spills his white human sperm all over her blue pantoran belly.
Meilsa then groans, “Ugh, I was almost there.” In a naggy voice.
Well that ain’t right. You can’t allow your daughter to be denied an orgasm like that.
“Eat her out.” You order your son.
Rowol’s eyes glaze over and he repeats, “I will eat her out.”
After he blinks, he dives with his head between his sister’s legs and starts licking Meilsa's well fucked pussy.
“Oh. Oh, Rowol.” Meilsa squeals in surprise. But then she accepts it and coos, “Ooooh, Rowol.”
She brings both her hands to the back of Rowol’s head and starts thrusting her hips as she starts fucking his mouth.
“Oh, yes. Rowol. I’m almost there. Just a bit more.” Meilsa moans.
You, of course, are also about to cum. You step a bit closer to your children, aim your dick at your daughter’s sperm covered belly and spill your own sperm all over it as well. Your semen mixes with that of your son, and soon your daughter’s belly is a white gooey mess. Just in time too, because that is when you hear her moan loudly in orgasm.

When Meilsa is done with her climax she looks at her belly and says, “Wow, so this is what sperm looks like.” She scoops some up with her hand and says, “I’ve never seen anything like this before.”
Rowol then looks at her smugly and says, “Would you like to see it again tomorrow?”
Meilsa smirks at her lover and says, “I’d love to.”
After that the two kiss again. That is when you take your que and leave. When you are in the hallway, you peek inside their room again and use your **** powers to order them, “You can acknowledge my presence again.”
As you walk away you hear both of them repeat your order.

You head back downstairs and wait until your children come down as well. You don’t have to wait long. When they come down, they have their clothes on properly. Meilsa has even washed her belly clean from all the sperm. They are surprised to see you. You then tell them both about finishing your work a day early as well as give Meilsa her art piece.

The next couple of months you kept a closer eye on your children. Plenty were the times you caught them in the act. Plenty did you watch them have sex. You always used your **** powers to make them perform certain sex acts, not just for your amusement but to improve their sex life. You even mind tricked your wives to be fine with ****, just in case they caught them too. Your kids should be grateful. But of course, you will never let them know how much you helped them. And once their studies are done, you will help them in making a little family of their own.