"Mr. Edwards was trying to get everyone on board," Young testified. "(He talked) over and over about the campaign."
She said Edwards also said that he didn't want his wife, Elizabeth, who had been diagnosed with cancer, to find out about the affair and child. Elizabeth Edwards died of breast cancer in December 2010.
Andrew Young did once claim to be the father of Hunter's child, though Edwards -- after losing his bid for the Democratic nomination -- acknowledged that the child was, in fact, his.
He is accused of concealing $725,000 in contributions from Mellon and more than $200,000 from Texas lawyer Baron, who has since died, from the public and from the Federal Election Commission by filing false and misleading campaign disclosure reports.
Edwards' attorneys have argued that Andrew Young was involved in a ruse to extract hundreds of thousands of dollars from donors for his personal use.
The former aide admitted during questioning by Edwards' attorney that he used campaign donations for his own benefit, including to fund construction of a home that included a pool and a theater.