Splitwise has some basic support for this now, depending on what you’re looking for. We now support multiple email addresses for a single account, so you can more easily share one account with multiple people.
However, we won’t automatically adjust how much you should owe as a “couple”. For example, if “Bob” adds an expense with “Sue and John’s Couple Account”, then the bill will be split 50/50 between those two Splitwise accounts. I can definitely see how it would be useful to automatically make Sue and John pay for 2 shares, but we’re unlikely to add that feature in the near future. For now, you can still work around this by manually using the “Split by shares” option when adding a bill, and assigning 2 shares to the relevant account.Dan Jackson commented
We're doing the same thing as Jaime, except for a shared bank account that we pay bills (like our mortgage) from. Being forced to create a "dummy" account was non-obvious & frustrating.
I'm stoked that there's enough flexibility to represent what we want to do: deposits to acct (from individual or from both of us) plus shared bills paid by the account or by an individual. However, the default settings are never right, and its tricky to get right every time.