Greville was the son of an obscure Lincolnshire squire. His prospects were transformed at the age of four, when his childless distant cousin, Sir Fulke Greville, adopted him as his heir. His grooming for this role included a careful education; indeed, according to Anthony Wood, he received some tuition at Cambridge University. When Sir Fulke was elevated to the peerage in 1621 as Baron Brooke of Beauchamp’s Court, his patent specified that Greville should inherit the title if Brooke died childless.
In early 1628 Greville was elected to Parliament at Warwick, where Lord Brooke was the dominant patron. On 4 Apr. he joined in the debate on supply, arguing for a grant of five subsidies and urging that recusants should be made to pay a double share. However, his return was voided on 31 May, following an inquiry into the Warwick election. By the time a by-election was held, Greville had become the 2nd Lord Brooke, and took his seat in the Lords instead.
During the following decade Greville mixed extensively with other puritan peers. He married a daughter of the 4th earl of Bedford, and became closely associated with the 2nd earl of Warwick (Sir Robert Rich*) and Viscount Saye and Sele through his involvement with the Providence Island Company. The town of Saybrook, Connecticut commemorates a joint colonizing venture in 1635.
