Thank you for citing a source. I would mention that at no point do any of the three articles substantiate the claim that ἀδελφός is being utilized in its secondary or even tertiary meaning in the context of MATT 13:55 et al. Staples and the like simply assert and hope you don't notice there's nothing there there.
Here are two Lexicons that are pretty standard scholarly texts regarding Greek. The second gives extensive examples from Ancient Greek literature showing the usage in Matt 13.55. I am sure some of our resident Greek scholars hereon CF can also comment.
(Louw-Nida)
10.49 ἀδελφόςa, οῦ m: a male having the same father and mother as the reference person—‘brother.’ εἶδεν δύο ἀδελφούς, Σίμωνα τὸν λεγόμενον Πέτρον καὶ Ἀνδρέαν τὸν ἀδελφὸν αὐτοῦ ‘he saw two brothers, Simon, called Peter, and his brother Andrew’ Mt 4:18. In a number of languages it is necessary to indicate the difference between older and younger brothers, and this can usually be done on the basis of Semitic usage, since the older brother was normally named first. Therefore, in Mt 4:18 one may translate ‘Simon and his younger brother Andrew.’
The interpretation of ἀδελφόςa in such passages as Mt 12:46; Mk 3:31; and Jn 2:12 as meaning ‘cousins’ (on the basis of a corresponding Hebrew term, which is used in certain cases to designate masculine relatives of various degrees) is not attested in Greek nor affirmed in the Greek-English lexicon edited by Arndt, Gingrich, and Danker. Such an interpretation depends primarily on ecclesiastical tradition.
Louw, J. P., & Nida, E. A. (1996). Greek-English lexicon of the New Testament: based on semantic domains (electronic ed. of the 2nd edition., Vol. 1, p. 117). New York: United Bible Societies.
(BDAG)
ἀδελφός, οῦ, ὁ (Hom. [ἀδελφεός]+; accord. to B-D-F §13; Schwyzer I 555; Mlt-H. II 58; PKatz, TLZ 83, ’58, 315f vocative ἄδελφε should be accented on the antepenult in Ac 9:17; 21:20 contrary to the practice of the editions; also GPt 2:5.)
① a male from the same womb as the reference pers., brother, Mt 1:2, 11; 4:18, 21 al.; τὸν ἀ. τ. ἴδιον J 1:41 (s. Jos., Ant. 11, 300). Of Jesus’ brothers (passages like Gen 13:8; 14:14; 24:48; 29:12; Lev 10:4; 1 Ch 9:6 do not establish the mng. ‘cousin’ for ἀ.; they only show that in rendering the Hebr. אָח ἀ. is used loosely in isolated cases to designate masc. relatives of various degrees. The case of ἀδελφή [q.v. 1] is similar Gen 24:59f; Tob 8:4, 7 [cp. 7:15]; Jos., Ant. 1, 211 [ἀδελφή = ἀδελφοῦ παῖς]. Sim. M. Ant., who [1, 14, 1] uses ἀ. for his brother-in-law Severus; the same use is found occas. in the pap: JCollins, TS 5, ’44, 484–94; s. VTscherikover HTR ’42, 25–44) Mt 12:46f; 13:55; Mk 3:31f; J 2:12; 7:3, 5; Ac 1:14; 1 Cor 9:5. James ὁ ἀδελφὸς τοῦ κυρίου Gal 1:19.
Arndt, W., Danker, F. W., Bauer, W., & Gingrich, F. W. (2000). A Greek-English lexicon of the New Testament and other early Christian literature (3rd ed., p. 18). Chicago: University of Chicago Press.