i understood your question but i guess my response perhaps was unclear. it's the check in agent where you check in who holds the cards and in my case, never had a problem. they applied an "obviously you're travelling together and therefore you are supposed to be able to share the baggage allowance" policy. but it seems to be at the first point of departure where that decision gets made.

you might call customer service to ask that they approve the baggage allowance and put it in the record. that sometimes helps in all matters. but i find it really sometimes is up to the luck of the draw: what sort of check in agent do you meet at the airport?

i've traveled similarly and always gotten the baggage allowance for myself and my travel companion, but i'm really not sure if it was courtesy or policy.

good luck!