Sir Nevill Catlin, sometimes written Catlyn or Catelyn, was an English landowner and politician from a Norfolk family long active in local and national affairs, his great-grandfather being Richard Catlin II and his father Richard Catlin IV. The Irish judge Sir Nathaniel Catlin was a first cousin once removed.
Baptised on 3 March 1634, he was the eldest surviving son of landowner and politician Richard Catlin (1583 – 1662) of Kirby Cane and his second wife Dorothy (1605 – 1672), daughter of landowner and politician Sir Henry Nevill of Billingbear and his wife Anne, daughter of Henry Killigrew. His father, who supported the King in the English Civil War, had been disabled from sitting in Parliament in 1644 and suffered sequestration of his estate, but was discharged without fine in 1647. His older half-brother Thomas Catlin died fighting for the royalist side in the Second Battle of Newbury in 1644 and his older half-sister Mary Catlin married Sir Edward Ward, 1st Baronet of Bexley. In 1650, he entered King's College, Cambridge.
In 1658 in London he married his first wife Dorothea, daughter of the judge and politician Sir Thomas Bedingfield and his wife Elizabeth, daughter of Charles Hoskins of Oxted. After her early death he married Elizabeth, daughter of Robert Houghton of Ranworth and his wife Elizabeth, daughter of Sir John Corbet, 1st Baronet, of Sprowston, but she died in 1681. His third marriage was to Mary, sister of Sir Charles Blois, 1st Baronet and daughter of Sir William Blois of Grundisburgh and his first wife Martha, daughter of Sir Robert Brooke of Cockfield. In the first two marriages there were three sons and a daughter, but none lived long.