Eileen Paisley, wife of the Democratic Unionist Party leader the Rev Ian Paisley and vice-president of the party, took her seat in the Lords yesterday as Baroness Paisley of St George's.
She will sit on the cross benches as an independent.
Lady Paisley is the fourth member of the Lords with a husband in the Commons.
The other couples are: Tories Peter Bottomley and Baroness Bottomley of Nettlestone; Tories Douglas Hogg and Baroness Hogg; and Lib Dems Alan Beith and Baroness Maddock.
Lady Paisley's sponsor peers were fellow cross-benchers former UUP leader Lord Molyneaux of Killead and former Commons Speaker Baroness Boothroyd.
Also sworn in yesterday was Scotland's Lord Advocate, Colin Boyd QC, who took his seat on the cross benches as Lord Boyd of Duncansby. - (PA)