I don't think we can assume anything about the monsters in terms of reproduction/proliferation. How many events where a human gets turned into a super-human have we observed? One in the intro? And we barely saw any of it.
It could be outside the norm that two monsters infected one person. Maybe the 3rd and the 4th figured out a special way to do it. Or maybe it is standard like you said and Jake was infected by another monster we don't know about as well. Or each one has its own vector or required conditions to spread their strain.
Definitely something to be observing as the game progresses- I'm dying to know.
When i say line(and line parent), i don't mean through reproduction. We saw the MC, Danica, and Alice turn from humans to Superhumans. Those 3 are all apart of different lines, turned by 3 different monsters. We know there's a difference of some kind between Jake and the MC's monster because the voice said that they don't listen to the 1st, which is in reference to Jake forcing the MC to forget.
There's no telling how many other lvl 1, 2, 3, and 4 Superhumans failed and turned into monsters over the years. That alone would produce plenty of monsters in the different lines of the numbered(parents), who can then turn people themselves. That's what i meant by line parent. We don't know all the details and this is mostly my speculation.
Oh, i nearly forgot but we did already know monsters can indeed reproduce sexually. From the dead end at the dorm party after the MC turns into a monster and fucks all of those women. Then there's this update when the monster in the sewer wanted us to impregnate her to give birth to powerful offspring. We don't know anymore details though.
As for Jake, i assumed after Ella gave him the pill, it lured a different monster(apart of the 1st line?). That would explain why Ella has different colored pills for different people. It could play apart in which type monster that she wants to be lured. She did say they do different things at her house.
Once again though, this is purely speculation on my part from what's shown and what i can recall. I could be mixing up details as this game has a huge amount of information. There could be some headcanon mixed in and flat out wrong stuff I'm saying so i apologize in advance if some stuff sounds off.
