Alexander I, Eventius, & Theodulus
Undoubtedly martyrs, but this article suggests that calling Alexander "Pope" is erroneous.
Pope St. Alexander I
Article on this pope, who died in 115 or 116. According to a tradition dating to the fifth century, Alexander was martyred, but it is possible that he has been confused with another St. Alexander who was indeed a martyr. From the Catholic Encyclopedia.
St. Alexander I
Brief essay, from "Popes Through the Ages."