The Autobus Review book "Northern and its subsidiaries" published in 1995 gives a very good history of Northern General from the 1880s up until the mid 1990s: https://www.abebooks.co.uk/servlet/BookD...1089679833&cm_sp=rec-_-pd_hw_i_1-_-bdp&reftag=pd_hw_i_1.

5 new subsidiaries were created in Jan 1991:
The Northern General Transport Co. Ltd. - Chester-le-Street, Consett & Stanley
The Tyneside Omnibus Co Ltd. (trading as South Tyne Buses) – South Shields
The Tynemouth & District Omnibus Co. (trading as Coastline Buses) – Percy Main & Wallsend
The Sunderland & District Omnibus Co. (trading as Wear Buses) – Sunderland, Philadelphia & Washington
The Gateshead & District Omnibus Co. (trading as Go-Ahead Gateshead) – Gateshead & Winlaton

During 1992 the new brands were introduced but Tyneside Omnibus Co Ltd. rebranded their ops as VFM rather than South Tyne Buses, and Northern General Transport Co. Ltd. rebranded their ops as Northern.