- PAUL BRIEN 729 LTDActive - Proposal to Strike off- 10057222 - Incorporated on 11 March 2016 
- DR. CONOR O'BRIEN- NI605401 - Incorporated on 6 December 2010 
- O'BRIEN & KIRK LTD- 10862380 - Incorporated on 12 July 2017 
- MARK A O’BRIEN LTDActive - Proposal to Strike off- 11207149 - Incorporated on 15 February 2018 
- JACK BRIEN LTDDisolved- 12228047 - Dissolved on 5 March 2024 
- MR.MR. LTDDisolved- 14252327 - Dissolved on 5 December 2023 
- AEDIFICIA CONSTRUCTION LTDDissolved- 04432043 - Dissolved on 21 September 2010 
- O'BRIEN WHEELER LIMITEDActive - Proposal to Strike off- 09692586 - Incorporated on 20 July 2015 
- VERMILION MANAGEMENT LTDDissolved- 09933044 - Dissolved on 28 May 2019 
- T.M. O'BRIEN LIMITED- 06507030 - Incorporated on 18 February 2008 
- MR MR2 LTD- 11218539 - Incorporated on 21 February 2018 
- MR & MR LTD- 16489396 - Incorporated on 2 June 2025 
- RONALD STANLEY LTDActive - Proposal to Strike off- 07728651 - Incorporated on 4 August 2011 
- RONALDO SPORTS LTDDisolved- 12879180 - Dissolved on 25 October 2022 
- RONALD LEE LIMITED- 09987174 - Incorporated on 4 February 2016 
- RONALD SOUTTER LTDDisolved- SC705994 - Dissolved on 9 January 2024 
- RONALD TEY LIMITED- NI721733 - Incorporated on 25 September 2024 
- WITT O'BRIEN'S LTD- 02261971 - Incorporated on 25 May 1988 
- TONY BRIEN LTDDissolved- 08208605 - Dissolved on 6 May 2014 
- O'BRIEN RAIL LTD.Active - Proposal to Strike off- 08600277 - Incorporated on 8 July 2013