404.364—When is a grandchild or stepgrandchild dependent?
If you are the insured's grandchild or stepgrandchild, as defined in § 404.358(a), you are considered dependent upon the insured if—
(b)
You were living with the insured in the United States and receiving at least one-half of your support from him or her for the year before he or she became entitled to old-age or disability benefits or died; or if the insured had a period of disability that lasted until he or she became entitled to benefits or died, for the year immediately before the month in which the period of disability began. If you were born during the 1-year period, the insured must have lived with you and provided at least one-half of your support for substantially all of the period that begins on the date of your birth. Paragraph (c) of this section explains when the substantially all requirement is met.
(c)
The “substantially all” requirement will be met if, at one of the times described in paragraph (b) of this section, the insured was living with you and providing at least one-half of your support, and any period during which he or she was not living with you and providing one-half of your support did not exceed the lesser of 3 months or one-half of the period beginning with the month of your birth.