And to suggest that they were traveling with Jesus as followers seems to ignore the fact that His brothers (in the Gospels) were unbelievers (remember John 7:2-10).
It never ceases to amuse me how people like yourself question every minor detail of our claims and demand that we Catholics jump through all sorts of hoops to prove our positions (as I just did above ;-)) while you apparently feel free to leap to wild and unsubstantiated conclusions. Your obvious mistake is the assumption that John 7:2-10 is referring to the same brothers who are listed by name in Matt 13:55 and Mark 6:3. Indeed, you assume (without warrant) that “brothers” refers to only the four men listed in Matt. 13:55 and Mark 6:3, rather than understanding that “brothers” (and “sisters”) was used to refer to Jesus’ entire clan.
The “brothers” (also rendered as “brethren”) in John 7 are not necessarily the four men listed in Matt 13 and Mark 6. As we know from Acts 1:14, some of Jesus’ so-called brothers did believe in Him and were among the faithful who awaited the coming of the Holy Spirit on Pentecost. So, the “brothers” cited in John 7 are apparently another group of brothers, and so distinct from the four listed in Matt. 13 and Mark 6, which just so happens to parallel the succession list of the first bishops of Jerusalem, which ran:
First, James (his literal sibling was Joseph/Joses); second, Simon; third Judas. I would submit to you that the reason that Matt.13:55 and Mark 6:3 lists these four brothers by name (i.e., four “brothers” out of a much larger group of “brothers” - all the male members of Jesus extended family) is because these happened to be the brothers who were known to be leaders in the early Christian community, and who were known to the original readers of the Gospels (see 1 Cor. 9:5). So, your problem (and it is a consistent problem with Evangelicals) is that you are reading Scripture with no knowledge its historical context – in this case, you are ignorant of the fact that it is speaking in terms of an entire clan of “brothers,” and so you impose your modern, American cultural sensibilities on the ancient Sacred Text and assume that Jesus came from a modern, nuclear family and that “brothers” must refer to a limited number of literal siblings therefore, the “brothers” in John 7 must be the same as those in Matt. 13 and Mark 6. However, Acts 1:19 and the consistent understanding of the Catholic Church both prove you wrong. Jesus had many, many “brothers.” He came from an extended tribal clan in Nazaeth, and James, Joseph, Simon, and Judas were merely four members of this clan – four members (perhaps along with others) who happened to believe in Him (per Acts 1:14).
As I have pointed out, Mr. Bonocore has made 2 assertions, but has provided no evidence to support them (not to mention these arguments have been addressed in part at the beginning of this post).
See above. Now, where is your proof that the “brothers” referred to in John 7 are the same four "brothers: referred to in Matt 13:55 and Mark 6:3? Also, where is your proof that Jesus had any literal siblings? Show me some, if you can. You’ve been shown plenty of proof that He did not.
The Catholic Legate – Lot of things here that are not related to the topic, so I won’t bother with it. I am curious, though. Do these articles reflect the “official” teaching of the Roman Catholic Church, or are they simply his interpretation of the “official” teachings of the Roman Catholic Church?
They are faithful to the teaching of the Magisterium of the Catholic Church and Sacred Tradition, yes. They do not claim to speak for the Magisterium of the Catholic Church (since they are not bishops), but all that is presented on the Catholic Legate (and other such Catholic apologetics sites) is in accord with what the Catholic Church formally teaches and intentionally faithful to it. Let’s put it this way: If Rome says “Jump,” they say, “How High?”
In other words, has the Roman Catholic Church “officially” declared that the James and Joseph of Matt 27:55 is the same James and Joseph mentioned in Matt 13:55?
Yes.

See The Catechism of the Catholic Church, Section 500, which reads:
500 Against this doctrine the objection is sometimes raised that the Bible mentions brothers and sisters of Jesus.157 The Church has always understood these passages as not referring to other children of the Virgin Mary. In fact James and Joseph, “brothers of Jesus”, are the sons of another Mary, a disciple of Christ, whom St. Matthew significantly calls “the other Mary”.158 They are close relations of Jesus, according to an Old Testament expression.159 "
If not, then wouldn’t that mean Mr. Bonocore is practising Protestantism?
Nice try. But the difference between Catholic Christians and Protestants is the issue of fundamental obedience. We have Christ-established authority over us, and we must be obedient to that authority when that authority speaks. This does not mean that we cannot have opinions or that we cannot use our own God-given ability to reason and discern things. Rather, it means that our personal subjective discernment is not the final authority. However, when it comes to Protestants, personal, subjective discernment IS your final authority; and this is why Protestants are divided into over 30,000 (and growing) sects, all with the same Bible, yet all interpreting it differently, for you have no final Christ-given authority to settle disputes and establish the Spirit-guided Truth.
I will pray for your return to orthodoxy and to the Truth.
Meanwhile, have a blessed Christmas!
Frances