Colossians 1:2 KJV
To the saints and faithful brethren in Christ which are at Colosse: Grace be unto you, and peace, from God our Father and the Lord Jesus Christ.
There are times in the Bible when the conjunction and is meant to weld two terms together as one as in a statement such as "the great God and our Saviour..." Other times it couples two distinct entities.
It is difficult to determine which is the case in this verse. Bible students have differing thoughts concerning it. I tend to take the position that, if God hasn't made something clear, then there is likely something to learn in all of the possibilities. Thus I would observe that:
Faithful brethren are saints.
Not that being faithful makes a person a saint for the term saint denotes one who has been saved and that is entirely the work of Jesus Christ. Faithfulness does not make a saint. However faithfulness can certainly help to distinguish a saint. All saints are brethren for that moment of salvation places each of us into the family of God and in brotherhood with Christ.
On the other hand,
Not all saints are faithful brethren
It is a fact sadly observed that some of those who have been saved are not as faithful in their faith as they ought to be.
· Some forsake the things of Christ for the world
· Some develop a contention and go their own way
· Some neglect the salvation that was given them
There is a relationship between the saints and the faithful brethren as they are both saved and, in this case, likely both members of this church. But there is also a sad disconnect that exists between those who are saved and not faithful and those who are saved but fully engaged in that which is Christ’s. Toward the faithful brethren Paul may thankfully pronounce grace and peace. Toward the saints who are not so faithful Paul may be praying that such grace and peace might one day be theirs as they become faithful.
 Titus 2:13 KJV
Looking for that blessed hope, and the glorious appearing of the great God and our Saviour Jesus Christ;
 A note in Jamison Fawcett and Brown reads, “.. ‘saints’ implies union with God, so ‘the faithful brethren’ union with Christian men [Bengel].” It is possible for a man to be united with God but to not be so united with Christian men.