Andrew, the brother of Simon Peter, was one of the two who heard John and followed Jesus. He first found his own brother Simon and told him, "We have found the Messiah" — which is translated Christ — Then he brought him to Jesus. Jesus looked at him and said, "You are Simon the son of John; you will be called Cephas" — which is translated Peter. (Jn 1:35-42)
https://bible.usccb.org/bible/readings/011424.cfm
Although the Fourth Gospel doesn’t mention anything about the Keys of the Kingdom of Heaven, and Peter’s eventual three denials of Jesus are really highlighted in the Passion Narrative, still Peter plays a significant role in the gospel along with the figure of the Beloved Disciple. But none of that would have happened if Andrew hadn’t told his brother about the Lord.