Traversing the children and pulling in the parent node for the child resolved this.
SELECT xtab.my_attr, xtab.my_attr_values
FROM my_table jx, xmltable('for $i in /root/a/b
return element r {
$i/../@attr,
$i/.
}'
PASSING jx.field_xml
COLUMNS my_attr path '@attr',
my_attr_values path 'b')xtab;