Use caution here, @bterrier; it matters who received the dividends and how they were reported by the brokerage firm.
If the estate got an EIN, reported it to the brokerage firm and received the dividends, the firm may issue a 1099 in the name of the estate and with that EIN. In that case, the estate may need to file a 1041 and issue a K-1 to the beneficiaries (siblings).
If the brokerage firm issued (or will issue) one 1099 to one of the siblings with the entire amount of dividends reported, then you have a nominee scenario.
The dividends need to be reported accordingly.
