but after deeper reading and contemplation, I’ve decided maybe they were not the only ones created at that time but they were still in fact the first created with a specific purpose. Maybe that’s why they were set a part and placed in the garden. idk but im relieved to know i’m not the only one who thought this

Adam and Eve had more kids sons and daughters and the kids took each other for wives (different dispensation) and they had kids

Cain was not cast out of Eden. Only Adam and Eve were cast out of the garden of Eden. Cain being casted out of his family happened well after Adam and Eve were casted out of the garden.

Adam and Eve were the first and only humans created. They had many children. We assume because we only hear about Cain and Abel at first that they were their only children until Seth. By time we hear of Cain and Abel they could be 100+ years old and Adam and Eve could have had 100 kids by then who married and had kids of their own. Population can grown pretty quickly.

The others God protected him from were his other siblings who would want to avenge their brothers death. This is also why God Specifically instructed the Israelites to always have a city of refuge for a murderer to protect them from the avenging family until righteous judge could be placed Cain was around 100yrs old and already married when he murdered his brother. Also it states that Cain was the first born son not the first born so Adam and Eve could have had daughters prior to Cain and Abel