On the eve of an international tour, Starr collapsed during a photo session at a studio in Barnes, London. Stricken with a 102 °F (39 °C) fever and tonsillitis, he was rushed to hospital, where Cox visited every day to help him recuperate. Afterwards they became a monogamous couple. On 20 January 1965, Starr proposed marriage to Cox at the Ad-Lib Club, above the Prince Charles Theatre, London.
After finding out that she was pregnant in late January 1965, 18-year-old Maureen married Starr at the Caxton Hall Register Office, London. The service was performed on 11 February 1965 by Barry Digweed, the superintendent registrar. Starr listed his father's profession as 'confectioner', and she listed her father as 'ship's steward'. Starr wrote that his profession was 'musician', but she left her profession blank.
The Starrs were living at 34 Montagu Square, Marylebone, when Epstein's accountant suggested that the group members should move to houses near his, in Esher. Lennon bought a house called Kenwood in St George's Hill, Weybridge, Harrison bought Kinfauns on a nearby estate in Esher, and on 24 July 1965, the Starrs bought Sunny Heights, on South Road, St George's Hill, for £30,000. Ken Partridge was asked to redesign the interior of the six-bedroomed house, incorporating a private pub above the garage, called The Flying Cow, which had a mirrored bar, pool table, jukebox, and a portrait of Lennon and McCartney on the wall. A TV was usually on in every single room, and a go-kart track was laid in the grounds. Although she cooked for the family, the Starrs had a nanny who lived in the house, and a cleaning woman who visited every day.
Zak Starkey was born on 13 September 1965, at Queen Charlotte's Maternity Hospital, the same day as the single "Yesterday" was released. She said at the time: "I'd like the baby to be like Ringo, but he need not necessarily follow in his father's footsteps". Starr said his son was "a little smasher", but also said, "I won't let Zak be a drummer", which was not to be, as his son later went on to play with The Who and Oasis. Jason Starkey was born on 19 August 1967, and daughter Lee Starkey was born on 11 November 1970.