The two link up with the Rams following their relegation to League One and have signed a two-year and a one-year deal respectively.
Hourihane, 31, joins the Derbyshire side after spending the last five-years at Villa Park.
The Republic of Ireland international became a firm favourite with the claret and blue faithful and was renowned for his wand of a left foot and the worldies he was able to unleash at any given moment.
After spending last season on loan at Sheffield United, Hourihane’s contract with Villa expired this summer and he was allowed to leave on a free.
In five-years in the West Midlands he made 151 appearances, scoring 29 goals and providing 23 assists.
Fellow former Villan, Chester, also links up with the League One side following his release from Stoke City.
The centre-back spent four-years at Villa Park between 2016-2020 and like Hourihane was a firm favourite, playing a big role in the squad that made it to the Championship play-off final in 2018 and the one that won promotion the following year.
He made 126 appearances for Villa, scoring 11 times and providing one assist.
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