Pretty sure you're wrong.
Then why doesn't your answer apply? I know for a fact that Jessica died after high school. Shannon left before the end of high school. Jessica's death had nothing to do with the MC getting together with Shannon in high school.
Your answer also implies that Shannon had 2 children before she met the MC. You may be right on this one but I doubt it.
I don't want to have to re-read the game but I don't remember Shannon having any kids when she was dating the MC in high school. If someone else will confirm that the reason the MC got together with Shannon in high school was because of her two kids I will be back to apologize.
It makes me wonder who the father was and where the kids were when Shannon was going to parties, hanging out at the pool, pursuing the MC or throwing shade at Jessica. I also wonder why the MC never mentions them, did Shannon give them up to their dad or something?
See, you actually answered why the MC got together with Shannon the second time. This is obvious because your explanation includes things that happened after the first breakup. If your response had included events or information from while the MC was in high school that would have implied an understanding of my post.
Answering a question that I did not ask implies that actually you did not understand just fine.