They have nothing in common and everything in common. They went separately up the Dublin Mountains to the Military Road after a woman and her son spotted skeletal remains there on Sunday.
They went in hope and fear. When they encountered on the bleak hillside, they embraced, united in their suffering. For the next few weeks, as the Forensic Science Laboratory goes to work on the fragments of what was once a human being, each will pray that the body is identified as that of their missing son.
Paul Byrne and Kenneth Fetherston simply disappeared, leaving family, toddlers and in one case a pregnant partner behind them. The mothers who hugged each other on the moorland yesterday believe them to have been murdered.
In the early weeks after the disappearance, in common with everybody whose son disappears, they hoped the young men had been "merely" abducted, or had an accident, but would come back. Over time, they abandoned that hope and came to terms with the probable reality of their child's death.
What they never abandoned was the hope that their son's body would be found. Because without that, a mother feels treacherous if she refuses to believe he is dead, but ridiculous if she persists, against the evidence, in believing him to be alive. If it feels unnatural for a young man to die before his parents do, it feels much more unnatural to have him slip away, his life and death unmarked by ritual or by place.
Humans have always needed both ritual and place for the dead. The ritual, allowing family and friends to remember a shared childhood, laughter, achievement and sadness. Allowing, in some cultures, the tearing of hair and rending of garments to express overwhelming grief. Allowing, in Ireland until half a century ago, the women of an area to "keen" making that high mournful wordless cry of loss that puts shivers up the spine. The ritual is important, with its songs, stories, pictures and relics of a lost life. Just as important is place. It's etched deep in the Irish psyche, the need to know the burial place of people we have loved, the need to believe that they've had "a decent Christian burial".
It may not be rational, but it is real, this sense that they will rest in peace if they sleep in a marked grave, visited by those who loved them. The playwright JM Synge registered this need in his play Riders To The Sea, where the mothers of fishermen out in all weathers in flimsy boats lived with the likelihood of their loss, but dreaded the possibility that their body would not be found.
Relatives of victims of the Troubles have begged former terrorist groups to reveal where they buried the dead, for the same reason: the need to know the worst, allied to the need to relinquish the remains to the welcoming soil. That's why two mothers trudged out to the foothills of the Dublin mountains this week, and why each of them understood immediately what the other was going through. Each had given up one hope (that of finding their son alive) and replaced it with a sadder hope (that of finding their son, dead).
The grim reality is that if one of those mothers gets her wish, the other will be spun loose to another long stretch of unfinished yearning, not knowing when or if her son's body will ever be found, not knowing when she can stand beside his coffin in a church filled with the scent of incense as a priest talks of what her boy was and why he mattered. One of the mothers will certainly have her hopes dashed. There's a real possibility both of them will be in that position, lying awake at night grieving that their beloved child lies lonely and lost in an unmarked shallow grave.