sorry for your loss. only one PR is allowed. choose. The balance due should come from the individual's estate.
if funds are not accessible, then the PR can submit a personal check or some other form of payment (I would not try direct debit). The payment becomes a claim against the estate and should be paid before the remaining assets are split among the beneficiaries.
Technically each of you should file form 56 with the IRS.
https://www.irs.gov/forms-pubs/about-form-56
