Complex sentence: Robert Tressell was born in Dublin, in Ireland, when it was part of the United Kingdom of Great Britain and Ireland, the illegitimate son of Samuel Croker, a senior member of the Royal Irish Constabulary.
Split into simpler sentences: Robert Tressell was born in Dublin, in Ireland (at the time, part of the United Kingdom). He was the illegitimate son of Samuel Croker, a senior member of the Royal Irish Constabulary.