The Cambridge Dictionary define "Saints":

(the title given to) a person who has received an official honor from the Christian, especially the Roman Catholic, Church for having lived in a good and holy way. The names of saints are sometimes used to name places and buildings:

• Saint Peter
• St. Andrew's school
• Saint Paul's Cathedral

-- Cambridge Dictionary

However, at the time when the book of Matthew and the epistles of Paul were written, the Roman Catholic Church did not exist yet and no titles were handed out to Christians. According to Cambridge's definition the church leadership determine whom or what may receive this special "title".

The original greek word that was translated to "saint" is:

No church has the right to choose what is "holy". It is God who determine what or whom are set apart (special) to Him.