In To Kill a Mockingbird, what family member was responsible for keeping the jury in deliberation and seeking a full acquittal?

In Chapter 23, Atticus and Jem discuss the outcome of the trial. Atticus mentions to Jem that it was on of his "Old Sarum friends" who kept the jury out so long. Jem realizes this means it was a Cunningham. Jem thinks this is odd because, as he says, “One minute they’re tryin‘ to kill him and the next they’re tryin’ to turn him loose… I’ll never understand those folks as long as I live.” Atticus adds that this Cunningham would be Walter Cunningham's double first cousin. 

Atticus tells Jem that he kept this Cunningham on the jury because any (white) man would go into the trial thinking about convicting Tom. In other words, it doesn't make that much difference who would be chosen for the jury because everyone in Maycomb has his own biases. Perhaps Atticus is thinking of Walter Cunningham's honesty. Atticus also might have also recalled how Walter decided to call off the mob that had come for Tom Robinson when he was being held in jail. If Walter has these moments of reason and honesty, maybe another Cunningham (i. e. the one on the jury) would as well. Atticus doesn't address this possibility but it might have crossed his mind.