The only reference to cousin used in the NT is in Colossians 4:10, the Greek word is anepsios, which is a noun masculine and means “cousin”. Nowhere else in the NT is the word cousin used, nor is there an example of the term brother being used as cousin, as far as I can see. The term in Greek is “adelphos” is used for brother and can mean used in a variety of contexts:
- a brother, whether born of the same two parents or only of the same father or mother
- having the same national ancestor, belonging to the same people, or countryman
- any fellow or man
- a fellow believer, united to another by the bond of affection
- an associate in employment or office
- brethren in Christ
1. his brothers by blood
2. all men
3. apostles
4. Christians, as those who are exalted to the same heavenly place
However; in Matthew 1:18 states: “Now the birth of Jesus Christ was as follows: when His mother Mary had been betrothed to Joseph,
before they came together she was found to be with child * by the Holy Spirit.” The Greek word for “came” is “synerchomai”, which is used in one of 2 ways:
- to come together
- to assemble
- of conjugal cohabitation
- to go (depart) or come with one, to accompany one
The context and use here should be obvious to all and the plain reading of Scripture that being related to the marriage covenant, the “conjugal cohabitation” is the meaning here.
Then add the use of “before”, tells us in no uncertain terms that they did come together as husband and wife, which when related to Matt 4:18 “Now as Jesus was walking by the Sea of Galilee, He saw two brothers, Simon who was called Peter, and Andrew his brother, casting a net into the sea; for they were fishermen.” We know that Peter and Andrew are blood brothers…I don’t know anyone who has ever questioned that.
Then go to Matt 12:47 "Someone said to Him, “Behold, Your mother and Your brothers are standing outside seeking to speak to You.” (Luke 8:20 is parallel passage) - we know it wasn’t His disciples, they were already with Him.
Also, Matt 13:55 "“Is not this the carpenter’s son? Is not His mother called Mary, and His brothers, James and Joseph and Simon and Judas?”
In addition Galatians 1:19 states “But I did not see any other of the apostles except James, the Lord’s brother”
In light of the plain reading and use of Greek terms, you can drawl your own conclusion based on the evidence. My conclusion is that Joseph and Mary had normal marital relations, which would honor God’s command concerning the marriage covenant.