Question: Who is Harry Mallaby-Deeley's sibling-in-law?

Knowledge 1: Harry Mallaby-Deeley
Sir Harry Deeley Mallaby-Deeley, 1st Baronet (27 October 1863, London – 4 February 1937, Cannes) was a British Conservative Party politician.Harry Deeley was educated at Shrewsbury School and Trinity College, Cambridge.His brother was the theatrical producer Frank Curzon.He was the founder and first President of Prince’s Golf Club at Mitcham.With his Cambridge University friend Percy Montagu Lucas he provided most of the capital to create new links at Sandwich, now Prince's Golf Club, Sandwich, the land being donated by the Earl of Guilford.The course was designed by Charles Hutchings, the 1902 Amateur Champion, and laid out between 1904 and 1906.In 1913 he purchased the whole of the Duke of Bedford's Covent Garden estate for £2m., having already been involved in the purchase of the Piccadilly Hotel and St. James's Court, Buckingham Gate.In 1922 he famously acquired control of the large estates of the cash-strapped Duke of Leinster during the latter's lifetime.Fitzgerald had previously sold Mallaby-Deeley his reversionary rights to the estate for a notional consideration, not expecting, as a younger son, to inherit.Deeley was elected Member of Parliament for Harrow in 1910 and for Willesden East in 1918, resigning in 1923.In 1922 he assumed the additional name of Mallaby, his mother's maiden name, by deed poll and was created a baronet (of Micham Court, Surrey). [SEP] Knowledge 2: Frank Curzon
Frank Curzon (17 September 1868 – 2 July 1927) was an English actor who became an important theatre manager, leasing the Royal Strand Theatre, Avenue Theatre, Criterion Theatre, Comedy Theatre, Prince of Wales Theatre and Wyndham's Theatre, among others.Curzon produced some of the most successful Edwardian musical comedies, including "A Chinese Honeymoon" (1903) and "Miss Hook of Holland" (1907; one of several successes starring his wife, Isabel Jay), and he later produced several plays starring Ivor Novello.Curzon was involved in a number of legal disputes, the most celebrated of which involved an audience member who refused to remove her hat.When Curzon prevented her from returning to her seat, she charged him with assault.Curzon won.Later in life, Curzon became a very successful racehorse breeder, and in 1927 his horse Call Boy won The Derby.
Knowledge 1: Harry Mallaby-Deeley
Sir Harry Deeley Mallaby-Deeley, 1st Baronet (27 October 1863, London – 4 February 1937, Cannes) was a British Conservative Party politician.Harry Deeley was educated at Shrewsbury School and Trinity College, Cambridge.His brother was the theatrical producer Frank Curzon.He was the founder and first President of Prince’s Golf Club at Mitcham.With his Cambridge University friend Percy Montagu Lucas he provided most of the capital to create new links at Sandwich, now Prince's Golf Club, Sandwich, the land being donated by the Earl of Guilford.The course was designed by Charles Hutchings, the 1902 Amateur Champion, and laid out between 1904 and 1906.In 1913 he purchased the whole of the Duke of Bedford's Covent Garden estate for £2m., having already been involved in the purchase of the Piccadilly Hotel and St. James's Court, Buckingham Gate.In 1922 he famously acquired control of the large estates of the cash-strapped Duke of Leinster during the latter's lifetime.Fitzgerald had previously sold Mallaby-Deeley his reversionary rights to the estate for a notional consideration, not expecting, as a younger son, to inherit.Deeley was elected Member of Parliament for Harrow in 1910 and for Willesden East in 1918, resigning in 1923.In 1922 he assumed the additional name of Mallaby, his mother's maiden name, by deed poll and was created a baronet (of Micham Court, Surrey). [SEP] Knowledge 2: Harry Calvert
Lieutenant General Sir Harry Calvert, 1st Baronet( March 1763 – 3 September 1826) was a British general.
Knowledge 1: Harry Mallaby-Deeley
Sir Harry Deeley Mallaby-Deeley, 1st Baronet (27 October 1863, London – 4 February 1937, Cannes) was a British Conservative Party politician.Harry Deeley was educated at Shrewsbury School and Trinity College, Cambridge.His brother was the theatrical producer Frank Curzon.He was the founder and first President of Prince’s Golf Club at Mitcham.With his Cambridge University friend Percy Montagu Lucas he provided most of the capital to create new links at Sandwich, now Prince's Golf Club, Sandwich, the land being donated by the Earl of Guilford.The course was designed by Charles Hutchings, the 1902 Amateur Champion, and laid out between 1904 and 1906.In 1913 he purchased the whole of the Duke of Bedford's Covent Garden estate for £2m., having already been involved in the purchase of the Piccadilly Hotel and St. James's Court, Buckingham Gate.In 1922 he famously acquired control of the large estates of the cash-strapped Duke of Leinster during the latter's lifetime.Fitzgerald had previously sold Mallaby-Deeley his reversionary rights to the estate for a notional consideration, not expecting, as a younger son, to inherit.Deeley was elected Member of Parliament for Harrow in 1910 and for Willesden East in 1918, resigning in 1923.In 1922 he assumed the additional name of Mallaby, his mother's maiden name, by deed poll and was created a baronet (of Micham Court, Surrey). [SEP] Knowledge 2: Sir Harry Burrard, 1st Baronet, of Lymington
General Sir Harry Burrard, 1st Baronet( 1 June 1755 – 17 October 1813) was a British soldier who fought in the American War of Independence, the French Revolutionary Wars and in the Peninsular War.

Answer: Isabel Jay