Here's the help file:

KINSHIP 'RACIAL KINSHIP' (3246)

Syntax: kinship <target> discuss <item>
kinship <target> pay <key>
kinship <target> trade <item> for <item>

The bonds between racial kin can be leveraged to trade for armors and weapons,
or even pay for keys. The bond of kinship is not strong enough to overcome
common sense, and they will want something of similar value to be convinced to
part with their equipment.

You can discuss with your kin to see if they would even be willing to part
with their item, and in the case of keys learn how much copper it would cost.

That makes it sound like its only possible to pay for keys. In fact, it's possible to pay for items as well. Either the help file is wrong, or the code is broken.

If the ability to trade coin for weapons and armor is intended, then it might be worth changing "kinship discuss" so that it tells the player how much coin the NPC needs in order to part with the item.

Also, it would be helpful if the help file spelled out the alignment restrictions for racial kinship activity, and whether half-races can make use of kinship at all.

Clarified as to key/item.