20 C.F.R. § 335.5
If an employee dies before filing one or more of the required forms, the form or forms may be filed by or in behalf of the person or persons to whom benefits would be payable pursuant to section 2(g) of the Railroad Unemployment Insurance Act. Such form or forms shall be filed within the time prescribed in § 335.4 of this part. Under these circumstances, the word "employee" as used in § 335.4(b) of this part and as used in § 335.4(d)(3) of this part shall include the individual or individuals by or in behalf of whom the form is filed. The order of distribution for benefits due but unpaid as of the date of an employee's death is the same as the order of distribution for annuities unpaid at death under the Railroad Retirement Act and may be found at § 234.31 of this title.
20 C.F.R. §335.5