Tyreese is a well known character in the books. I wont go into any real detail unless someone wants to know more. However, Ill just say that in the book, Tyreese (and his group) originally met up with Rick (and his group) while they were on the road. This is when Ricks group were still living out of the Winnebago and were transitioning from Hershels farm (due to a falling out) but had not yet found the prison. So Tyreese helped clear the prison.
Tyreeses group consisted of his daughter and his daughters boyfriend. If there were others I forget their relation and significance.
Morgan is currently an active character / group member in the book so it makes sense that he would make an appearance in the show at some point. It feels way too early for that in the show since a lot still should happen before he reappears. However, Tyreese seems very late so events are somewhat out of order