Complex sentence: Whilst the true identity of Brian's father was never made public, his mother was a teenage waitress named Frances Connolly who left him in a Glasgow hospital as an infant whilst possibly suffering effects of meningitis.
Split into simpler sentences: Whilst the true identity of Brian's father was never made public, his mother was a teenaged waitress named Frances Connolly. He was left in a Glasgow hospital by his mother as an infant whilst possibly suffering effects of meningitis.