A close reading of the literary context of the phrase “flesh and bone” vis-à-vis "brothers" as biological family in Luke-Acts, beginning with Luke 24:32-36:
“They asked each other, “Were not our hearts burning within us as He spoke with us on the road and opened the Scriptures to us?” And they got up that very hour and returned to Jerusalem. There they found the Eleven and those with them, gathered together and saying, “The Lord has indeed risen and has appeared to Simon!” Then the two told (drew out, ἐξηγοῦντο) what had happened on the road, and how they had recognized Jesus in the breaking of the bread. While they were describing these events…”
The two on the road, one of them named Cleopas (Lk. 24:18) were pondering a resurrection appearance of Jesus, and immediately (“that very hour” αὐτῇ τῇ ὥρᾳ) they returned to Jerusalem (εἰς Ἱερουσαλήμ) where they found “the eleven” and “those with them” (who?) discussing yet another resurrection appearance--this one experienced by “Simon” (Peter). It was while they were conferring about these resurrection appearances that it happened--the appearance in “flesh and bone" (Luke 24:36-39):
“While they were describing these events, Jesus Himself stood among them and said, “Peace be with you.” But they were startled and frightened, thinking they had seen a spirit. “Why are you troubled,” Jesus asked, “and why do doubts arise in your hearts? Look at My hands and My feet. It is I Myself. Touch Me and see—for a spirit does not have flesh and bones, as you see I have.” And when He had said this, He showed them His hands and feet.”
Who specifically, we may ask, was there in that particular gathering? Acts 1:13-14 provides a closer look at “the Eleven” along with some others who were with them in the place they had gathered:
“...the upper room, where they were staying, Peter and John and James and Andrew, Philip and Thomas, Bartholomew and Matthew, James the son of Alphaeus and Simon the Zealot and Judas the son of James. All these with one accord were devoting themselves to prayer, together with the women and Mary the mother of Jesus, and his brothers.”
If this expanded image from Acts applies to those who were there previously in Luke, the appearance in “flesh and bone” took place during a discussion of two resurrection appearances in a group that included Peter and the biological family of Jesus--“Mary the mother of Jesus, and his brothers. (σὺν τοῖς ἀδελφοῖς αὐτοῦ)” i.e. The “flesh-and-bone” brothers (in the LXX sense of the phrase, viewtopic.php?f=6&t=5317#p35733).