Don’t think so. Someone who can call himself a “brother of Jesus” at this point in history would be one of two sets; group 1-biologically affiliated or group 2- theologically affiliated. Group 1 has a small set size. Group 2 has a much larger set size. Then you have the small number of extant ossuaries. I think it’s more probable that the group with more members would be more likely to have a surviving ossuary than the group with fewer members.
BTW even if this is a bio-brother/cousin that says nothing about Mary. This ossuary can’t answer that question.
That goes back to my question from earlier: Where are the other ossuaries with the title, “brother of Yeshua” written on them? You’re making a claim that this was a common practice in the 1st-2nd Century Church. Prove it.