I found them in the 1861 Census in Ross.
1861 Census, Ross Borough, Herefordshire, Wales? England? - See Inman Census File for Copy
Thomas Hinman, Male, 33, Head, Born Ross, Herefordshire
Maryanne Hinman, Female, 37, Wife, Born Ross, Herefordshire
George Hinman, Male, 11, Son, Born Ross, Herefordshire
Elizabeth Hinman, Female, 9, Dau., Born Ross, Herefordshire
Mary A. Hinman, Female, 1, Dau., Born Ross, Hereforshire
Mary Ann's maiden name was Garraway. She is the daughter of William Garraway and Ann Constant.
I agree with you that Thomas is the son of Thomas and Mary Anne (Whitney) Hinman/Inman
Caroline