St. Ignatius of Antioch was one of the earliest bishops of the Church, being a disciple of St. John the Evangelist. One of his chief concerns at the time was Christian unity.
He wrote several letters. and in many of them he explains his desire for unity.
For example, in his Letter to the Magnesians, St. Ignatius instructs the people to do everything in union with the local bishop and priests.
As therefore the Lord did nothing without the Father, being united to Him, neither by Himself nor by the apostles, so neither do anything without the bishop and presbyters. Neither endeavour that anything appear reasonable and proper to yourselves apart; but being come together into the same place, let there be one prayer, one supplication, one mind, one hope, in love and in joy undefiled. There is one Jesus Christ, than whom nothing is more excellent. Therefore run together as into one temple of God, as to one altar, as to one Jesus Christ, who came forth from one Father, and is with and has gone to one.
St. Ignatius expressed a similar desire for unity in his Letter to the Ephesians.
[I]nasmuch as love suffers me not to be silent in regard to you, I have therefore taken upon me first to exhort you that you would all run together in accordance with the will of God. For even Jesus Christ, our inseparable life, is the [manifested] will of the Father; as also bishops, settled everywhere to the utmost bounds [of the earth], are so by the will of Jesus Christ.
Unity is a topic that the Church has struggled with since the very beginning. If we are looking for a particular patron for Church unity, St. Ignatius would be a great intercessor.