Born and raised in Cork, Twomey first played hurling to a high standard as a student at Presentation Brothers College (PBC).
He was part of the extended panel when the club's senior football team won the Cork PSFC title after a defeat of Clonakilty in 2021.
[6] He was again part of the panel when St Finbarr's beat Austin Stacks by 2-09 to 1-10 to claim the subsequent Munster Club SFC title.
[7] In October 2022, Twomey was at midfield when St Finbarr's beat Blackrock by 2-14 to 1-07 to win their first Cork PSHC title in 19 years.
Success in this grade was immediate with Twomey claiming Munster and All-Ireland U20HC medals as a member of the extended panel in 2020 after respective defeats of Tipperary and Dublin.