two more takes on Philemon and Onesimus as literal (half) brothers

In Philemon 16:




no longer    as a slave,
but more than a slave,
                     as a dear brother.
 He is very dear to me
        but even dearer to you,
                    both in the flesh
                    and  in the Lord


Most see
                                                             "brother" as metaphorical 
and    
                                      "slave" as literal.

Others see it exactly the other way around:

                                       "slave" as metaphorical 
and                                        
                                                                     "brother" as literal.

Usually you hear that Onesimus couldn't be both Philemon's literal slave
                                      and                                                         literal brother..
                                                                ...as no one would have their brother
                                                                                                         as a slave..

But what if a wrench/fuzzy set is thrown into all this? A half-brother...and somewhat a slave,,

1)Paul Welton:

There’s an even bigger complication, if that’s possible! Listen again to what Paul writes in verses 15 and 16:

Perhaps this is the reason he [Onesimus] was separated from you for a while, so that you might have him back for ever, no longer as a slave but as more than a slave, a beloved brother—especially to me but how much more to you, both in the flesh and in the Lord.

“A beloved brother…both in the flesh and in the Lord.” Onesimus was Philemon’s slave; how could he also be his ‘brother in the flesh’?
The most convincing answer to that question is really quite distressing to me. It is this: a slave was the slaveowner’s property, and had to do whatever the owner wanted. That included a slave submitting to the owner’s sexual demands. If the master wanted sex, the slave had no choice but to submit. It is likely that Onesimus was Philemon’s brother in the flesh because while his mother was a slave, Philemon’s father was also his father. In other words, Philemon and Onesimus were most probably half-brothers.
If that is true, they had a complicated relationship. They were master and slave, and shared the same father. One was a person, a citizen; one was property. But now they were brothers in Christ, and Paul wanted Philemon to welcome Onesimus as he would welcome Paul.
Paul wants Philemon to receive Onesimus as a brother, a fellow Christian, and a human being. No longer could Onesimus be merely ‘useful’ property.  link

2)D. Edmond Hiebert (one of the coolest guys I ever met):

:In the flesh Philemon has the brother as a slave, and in the Lord the slave as a brother; how greatly, therefore, must he, in view of the mutual connection and interpenetratiion of the two relations, have him as a beloved brother!" (Meyer)

The reference to Onesismus as Philemon's brother "in the flesh"  has raised the conjecture that Philemon and Onesimus are physically  related, the latter being born of a slave mother, hence having the status of a slave.  But Paul's use of the word "brother" affords no proof of such a natural relationship..

Paul does not say a word against the institution of slavery.  He does not intefere with the civil relationships, but he does deal with the moral and spiritual relationships.  He does not say "no longer a servant," but "no longer as a servant."  He does not make a frontal attack on the inhuman institution; he rather injects the dynamic of Christian love and allows it to transform the conditions of temporal servitude into a holy brotherhood.  It was this principle which effected the eventual abolition of slavery as a legal institution
p, 116, Titus and Philemon, emphasis mine

Related:

Philemon: alternative interpretations

Philemon and Onesimus as literal brothers