4 To Titus, a true son in our common faith: Grace, mercy, and peace from God the Father and the Lord Jesus Christ our Savior.
a true [genuine] son
Paul led Titus to Christ. He was a “true” or genuine Christian. There is no record of Paul’s family in the New Testament. The Jewish historian Josephus did said that a person of Sanhedrin had to be married. Titus was not Paul’s physical son but his spiritual son.
People we lead to Christ are our spiritual sons.
Whenever you lead people to Christ, they are your spiritual sons. Would you not like to be the person who led Billy Graham to Christ? What a spiritual son that would be!