Initially betrothed to his first cousin Catherine Venables, who died young in 1680, he married Anne Ferrers on 27 September 1688.
Shirley visited the family estate in Ireland (a moiety of the Barony of Farney, in County Monaghan) in the summer of 1698.
He solicited the support of Sir Walter Bagot, 3rd Baronet, who had sat for the county until 1695, and his son Edward, but this forward proposal (the Staffordshire gentry had historically met and chosen candidates by consensus, to avoid the cost of a contested election) backfired.
Edward had his own designs on the seat, and he wrote to many of the local gentry to inform them of Shirley's breach of protocol, asking them not to pledge their support until a meeting could be held.
Lord Ferrers, though a Tory, obtained the interest of the Whig Dukes of Shrewsbury and Newcastle on Robert's behalf, suggesting a fluid political affiliation.