score:1
How about American Airlines? https://www.aa.com/i18nForward.do?locale=en_GB&p=/AAdvantage/requestingMiles.jsp
Or Iberia? https://www.iberia.com/gb/iberiaplus/not-shown-avios/
I would not recommend Qantas as it is one of the worst programs (they even try to charge some people to join) and ask a lot of miles for award flights.
Iberia Avios are transferable to BA. BA also has a household pooling option: https://www.flystein.com/biggest-mistake-frequent-flyers-make/
Upvote:5
Depends how far back, but members of Australian Frequent Flyer group claim that Qantas, a member of OneWorld, allow you to claim for flights up to 30 days before joining.
This is backed up on an article on Australian Business Traveller.