David S cott and Samuel Hamlet may have been partners. You'll find Samule Hamlett on the 1850 Bibb Co. AL Census living with his wife and child. Looks like they might have fallen on hard times since they're living with the Scott family in 1860.
You can't tell from the 1860 Census if Eliza was David's wife or daughter. You'll have to find that from other sources.
Isabel could have been a boarder or household help. Successful Searching!