> dóttir Þormóðar skafta (skaptr?),

The daughter of Þormóðr skafti

> Ölvissonar barnakarls
> son of Ölvis Man-of-Children (?).

Landnámabók explains his nickname thusly:

Ölvir barnakarl hét maður ágætur í Noregi; hann var víkingur mikill.
Hann lét eigi henda börn á spjótaoddum, sem þá var víkingum títt; því
var hann barnakarl kallaður.

"There was a famous man in Norway called Olvir Children's Man. He was
a great viking. He didn't have children caught on the points of
spears, as was usual for vikings at that time. For that reason, he
was called Children's Man."

Hence MM & HP's "Child-Sparer." What an outlandishly nice viking!
Odin alone knows what his fellow sea-rovers made of that little
eccentricity.

Patricia wrote: "I wonder if this is the Same Olvir whose sword was
now in Gunnar's hands - as Olvi's gift."

Different one. The Ölvir who gave Gunnar his sword was the man he
stayed with in Norway. According to this, Ölvir barnakarl lived
several generations earlier.