The Bible is pretty clear that Jesus had brothers, but that is heresy to Catholics.
Absolutely.
And the semantics rationalization just does not wash.
They would have it that the authors only had use of one word that meant two things about relatives. That’s nonsense.
Why in the world would that be heresy to Catholics?
Ever read the Protoevangelium of James? Yes, I know it's not part of the Canon and, so, I don't assert it as a scriptural source (rather an early non-canonical source that reflects the views of, at least, some of the Church in the second century AD -- that's a couple of centuries before Constantine for the conspiracy theorists in the audience)
Anyway, if you haven't, you can Google it yourself. If you read that, you'll find a potential explanation contained therein that is totally consistent with scripture (what is actually written there, not the explanations given by you and your teachers). If, in fact, it is correct in its explanation, it shows how the term "brothers of Jesus" could be applied AND also demonstrates the perpetual virginity of the Blessed Mother.
Heresy to Catholics? Hardly. Only a point of salivation for a Protestant.
Spiritual brothers. The Bible talks about Spiritual Brothers!
Is the word “cousin” ever used in the Bible? I don’t think it is, so why can’t “brothers’ just be a collective word for “kin”.