While it's often credited to Cyril alone, the two brothers worked together to develop the alphabet for the Slavic people.
Here's a breakdown:
* Cyril (827-869) was a Byzantine scholar who, with his brother Methodius, was sent to the Great Moravian Empire to spread Christianity.
* Methodius (815-885) was the elder brother and served as a bishop.
The two brothers developed the Glagolitic script first, but Cyril later adapted it to create the Cyrillic alphabet based on the Greek alphabet. This alphabet was designed to translate the Bible and religious texts into the Old Church Slavonic language.
It's important to note that the Cyrillic alphabet has evolved over time, with different variations and modifications being introduced by various cultures and languages that adopted it.