Second member from same household for a discount

I am setting up a members area for a not for profit who want to offer a discount to second members of the same household so for example the first member pays £10 and the second member of the same household pays £5 for full membership.

I need a way to tie these two memberships together so that the start and end dates are the same and they can be paid for at the same time.

Can this be done using the membership plugin (or can I modify it to make it do this) or should I be looking elsewhere for this functionality?