Following Ann Renshaw's remarriage the family prospered and came to own a fuel depot, stock and station agency and butchery in the town.

[1] Renshaw was educated at Binnaway Central School, Patrician Brothers at Orange (where he lived with his grandmother), and then Holy Cross College at Ryde in north-western Sydney.

He was supported by the Premier, William McKell, who realised that Renshaw's strong local identity and links to the farming community would help him in an election.

Renshaw stood in the 1941 election, winning the seat from the Country Party member, Alfred Yeo, who had held Castlereagh for the previous nine years.

Relying upon his strong knowledge of agricultural and rural issues, he aggressively prosecuted the case for Labor's policy of compulsory resumption of large properties so that they could be subdivided.

Impressed by his handling of the closer settlement debate, the new Premier Joe Cahill promoted Renshaw to Secretary for Public Works in 1952.

"[7] Renshaw found it difficult to connect with urban voters, and his problems in adjusting to the new pressures of television only exacerbated his electoral failings.

Nevertheless, Renshaw remained an important figure both in the state parliament and in Labor's ruling circles; he served as Treasurer during the first four years (1976–80) of Neville Wran's administration.

On 12 November 1942 Renshaw married Hilda May Wall, at St Canice's Catholic Church, Elizabeth Bay; by her he had a son.

His second wife, whom he married on 11 April 1966 at Holy Cross Catholic Church, Woollahra, was Marjorie (Meg) Mackay née Nolan (who had four children in total: one by Renshaw, three by a previous marriage).