John Gill Commentary Luke 6:15

"and Matthew and Thomas, and James [the son] of Alphaeus, and Simon who was called the Zealot," — Luke 6:15 (ASV)

Matthew and Thomas
The first of these was a publican, and who also was called Levi; and the latter had besides the name of Didymus, and was he that was so unbelieving of Christ's resurrection:

James the son of Alphaeus ;
sometimes called James the less, and the brother of our Lord: and

Simon called Zelotes ;
or the Canaanite; (See Gill on Matthew 10:4).