I looked at the marriage records of Cyrus and Lena's sons today while in Augusta. Guy F. Hill married 22 Aug. 1893 in Brunswick Edith E. Groves, daughter of George F. Groves and Harriett A. Boynton. Lee J. Hill married 26 Aug. 1896 in Brunswick Jessie L. Cantello, daughter of Hector Cantello and Christine McThee.
Both records give the groom's parents' names as Cyrus F. Hill, b. Augusta, and Lena F. Allen, b. San Francisco.
I have copy of Obit for Frank Hill Sr and It also list Lena Goss as his mother - I think there may have been a divorce in that family because it list frank hill as having a step sister.
Here's the death record of Frank's half sister Maude. It looks like she was Cyrus' daughter by his second wife, Margaret McManus, whom he married in 1885.