Kathleen Harrington Kennedy Townsend, the daughter of Robert F. Kennedy and Maryland's former lieutenant governor, posted a photo of herself meeting with Bush on her private Facebook page, with the caption, "The President told me he's voting for Hillary!!" over the weekend, Politico reported.
A Bush spokesman declined to comment on the photo, saying the 41st president's vote would remain private. He is 92.
Townsend, a Democrat, told Politico on Monday that she met the former president while she was in Maine.
The photo and comment were posted to her personal Facebook page, which was not viewable by the public.
Both Bush, former first lady Barbara Bush and their son, former President George W. Bush, campaigned for Jeb Bush during the Republican primary. None appeared at the Republican National Convention in July and none have come forward to endorse Donald Trump since he claimed the party's nomination.