Just a hypothesis, but is it possible that the female lead will become pregnant?

I'm honestly scared for her to have kids

oh shit-

I doubt it honestly. That would be a whole other curve ball that strides away from the progressing story.
From the way everything’s been moving, there seems to be a lot more that will happen but not a bun in the oven, not this soon..they’re not even lovers—plus, there’s a possibility protection was used

Since the ML and Little Sister share the same personality, just different approaches, I doubt that would go well. ML would only be happy to tie our MC to him but get frustrated when she says no because her sister isn't of age to take over the estate. He's also still cursed so unless it breaks with him, his offspring will be in the same position and he wouldn't want to see that happen like what he witnessed as a boy. He is only reassured now because MC has the potential to cure him.

LS already doesn't like having to share her sister's attention so a baby would at best be tolerated. So until LS realizes MC knows exactly what she's like and that her attitude is something she treasures so she doesn't have to hide it, she won't have the room to mature to let MC fulfill other life milestones in the slightest.