There has been a lot of confusion about Dr. John Rees Gabe.
Here is some stuff I collected in the course of writing the second edition of "Deconstructing Jack: The Secret History of the Whitechapel Murders." It is surplus to my requirements, so please use it as you see fit.
DOCTOR JOHN REES GABE AND HIS TWIN BROTHER—
In 1846, in Merthyr Tydfil, Rees Gabe [b.1822/3] married Ann Harries [b.1826].
25th August 1849. "Rees Gabe, late of Pontmorlais, Merthyr Tydfil, Glamorgan, Cordwainer [shoemaker]—in the gaol of Cardiff." London Gazette. Insolvent Debtors.
In the 1851 Census [name transcribed as Gape], Rees Gabe was a Boot & Shoemaker. He and Ann had three children — Lemuel , William , and Mary Ann .
On 1st November 1853, at Pontmorlais, Merthyr Tydfil, Ann Gabe, wife of Rees Gabe, now Innkeeper of the Lord Raglan, 119 High Street, Merthyr Tydfil, gave birth to twins, John Rees Gabe and Benjamin Gabe.
The family appears to have moved establishments.
Merthyr Telegraph, 6th December 1856—
And then moved back again.
Merthyr Telegraph, 28th July 1860—
John Bernard Gabe [b. 1854] was the son of Merthyr Tydfil builder, John Gabe [b. 1802].
John Gabe [builder] was the brother of Innkeeper Rees Gabe. There was 20 years between their ages. See 1897 funeral below.
The 1861 Census lists seven children—Mary Anne , William , Joseph , Benjamin , John , Elizabeth , and Henry . No mention of Lemuel; but a Lemuel Gabe died in Birmingham, 1925, aged 79, [b.1846], which is a close match.
22nd June 1861—
In the 1871 Census, the twins are now aged 16.
John Rees Gabe was a Clerk, and Benjamin Gabe a Plasterer.
Their siblings are—Elizabeth , Henry , Rees , Rachel .
No mention of Mary Anne [now 21, she married in 1868], William [now 23, he married in 1866], Joseph [now 18, he didn't marry until 1874].
April 17th 1875. John Rees Gabe, Middlesex Hospital. Passed primary examination for Royal College of Surgeons of England.
In 1877, at Pontardawe, John Bernard Gabe married Annie Rosser.
On 17th November 1879, John Bernard Gabe, L.S.A., Merthy Tydfil, was admitted to the Royal College of Surgeons of England.
On 30th March 1880 "John Rees Gabe M.R.C.S.E. and L.S.A.L." married Marion Lucy Senior Fincham at St. Stephen's Church, Hounslow.
3rd February 1881, at Apothecaries' Hall, London, John Bernard Gabe, Morriston, near Swansea, passed his examination in the Science and Practice of Medicine, and received a certificate to practice
In the 1881 Census, the occupation of John B[ernard] Gabe is given as General Practitioner LSA [Licentiate of the Society of Apothecaries]. He is married to Annie Gabe and living with his mother-in-law Margaret Rosser and her two children, Jenny and John]. They have no children of their own.
1881 John Rees Gabe is living at 21 Church Street, Spitalfields, E. International Medical Congress member.
On Tuesday, September 6th, 1881, the Foundation Stone of the Masonic Hall, Merthyr Tydfil, was laid with Masonic honours. The architect was "J. Gabe, Builder."
1884 Medical Directory. Gabe, John Bernard, The Laurels, Morriston, Swansea—L.F.P.S. Glasg. and L.M. 1881: L.S.A. Lond. 1881; (Middlx.); Mem. Brit. Med. Assoc.' Surg. Collieries, Foundries, and Chem. Works; Med. Ref. Star, Gen. City, and other Assur. Socs.
1885: John Rees Gabe passes the M.D. Brux. [Brussels] examination with distinction.
1885: John Rees Gabe, MD, MRCS, LSA, Listed as a Fellow of the British Gynaecological Society. Address, 16 Mecklenburgh Square.
The Times, 8th April 1885—
Announcement of the death of Harry [Henry] Gabe aged 24 at the home of his brother J.R. Gabe, 16 Mecklenburgh Square. Medical student at the London Hospital. Family living at Cefn Coed-y-Cymmer, South Wales.
1887. John Rees Gabe, London Hospital E.— LSA 1876 [Lond. Hosp.]. Clinical Assistant London Hospital. Late Assistant Resident Medical Officer Stamford Hill &c. Disp. and Junior House Surgeon, Poplar Hospital.
The Times, March 29th 1888—
John Rees Gabe is reported as surgeon to the Society for the Prevention of Cruelty to Young Children.
In the 1891 Census, [name transcribed as Jabe] the occupation of John B[ernard] Gabe is given as Surgeon. [He is still married to Annie Gabe and living with his mother-in-law Margaret Rosser and her two children, Jeannie and John]. They live at Llangyfelach Road, Swansea. They have three children—Howell  wrongly transcribed as a servant, Beryl  and Thana .
In the 1891 Census, the occupation of John R[ees] Gabe of Mecklenburgh Square, London, is "Only Registered Medical Man General Practitioner." He is living with his wife, Marion, and their three children, Caroline , Winifred  and Ivor 
1892. John Rees Gabe's wife, Marion Lucy Senior Gabe, dies, age 37.
1895 [approx.] John Bernard Gabe becomes a trustee of the Libanus Church.
9th March 1897. John Gabe [builder] dies, aged 82. The funeral is held on Monday 15th March.
John Bernard Gabe, from Morriston, is reported to be his son.
Rees Gabe is reported to be his brother.
Amongst the many Gabes attending the funeral, travelling in the third carriage, is "Dr. Gabe, London.” Being the son of Rees Gabe, this makes him the nephew of John Gabe [builder].
In 1898, John Bernard Gabe filed a US Patent—
UNITED STATES PATENT OFFICE.
JOHN B. GABE, OF SWANSEA, ENGLAND [sic].
DESIGN FOR A THERMOMETER-CASE;
SPECIFICATION forming part of Design No. 30,225, dated February 21, 1899. Application filed November 19, 1898. Serial No. 696,938. Term of patent 14 years.
To all whom it may concern:
Be it known that I, JOHN BERNARD GABE, a subject of the Queen of Great Britain, residing at Morriston, R.S.O., Swansea, in the county of Glamorgan, England, have invented and produced a new and original Design for Thermometer-Cases, of which the following is a full, clear, and exact description, reference being had to the accompanying drawings, forming part thereof.
My new design is illustrated in the accompanying drawings, in Which Figure 1 is a face View, and Fig. 2 an edge or side View, of the thermometer-case.
In the 1901 Census, the occupation of John B[ernard] Gabe is given as Surgeon. [He is married to Annie Gabe. Mother-in-law Margaret Rosser is now deceased , and her two children have moved on. They now have five children—Howell , Bergh , Thaisa , Vincent , and Leslie [Joseph] .
There is no 1901 Census entry for John Rees Gabe, nor his daughters Caroline and Winifred Agnes, who, in 1919, registered with the Royal British Nurses Association. His son, Ivor Stanley , was a student. He went on to become a Royal Navy Surgeon Commander in Australia. In 1943, he died in London, age 58. His next of kin was his wife, Ada Gabe, ChalÍt Blanc, St. Jean-de-luz, France.
On 3rd April 1902, Dr. John Bernard Gabe, of Morriston, South Wales, was entertained by a number of his fellow citizens at a banquet, when an address expressing high appreciation of his services during a professional career in the town of twenty-eight years was offered to him. A presentation was made at the same time, consisting of a silver tea and coffee service, silver kettle and tea tray, a case of twelve silver spoons and sugar tongs, a silver-mounted ebony walking stick, and an album with the autographs of the subscribers.
In 1907, John Bernard Gabe came before the General Medical Council [see cutting]. He was cleared in June 1908.
John Bernard Gabe died in Swansea, 6th July 1908, age 54 [b. 1854].
Leslie Joseph Gabe (1898-1923). M.R.C.S., L.R.C.P. (Eng.). [Epsom College 1910-1915. Rugby XV] was the son of Dr John Bernard Gabe, of Morriston, South Wales. He received his medical education at the Middlesex Hospital. During the First World War he served as a Naval Rating (1915-1918) and died in 1923 as a result of active service. He was aged 25 years.
Here is Leslie Joseph Gabe's headstone—
John Rees Gabe died on 2nd March 1920, age 67 [b.1853].
John Rees Gabe's twin brother, Benjamin Gabe, a plasterer, died in Pontypridd, 1925, age 72 [b. 1853].