1871 Census records has him age 26 (born about 1845) from Hanover.
1881 Aged 36, at 45 Ascot St
1891 Aged 46, at 45 Ascot St

Name is confirmed on declaration of Doris's brith certificate, which also shows both spellings of Dittmer/Dettmer.

Marriage record has his full name as Johann Heinrich C Dittmer.

Cannot be the Johann Heinrich Dettmer, born 27 AUG 1847 in Wolthausen, Hannover, Preussen as he married Marie Dorothee Alwine Meine on 02 APR 1875 at Winsen, Schleswig-Holstein, Preussen.

Deaths Sep 1912   (50%)
DITTMER  John H C  67  Toxteth Park  8b 192

There's another John Henry Dittmer who died in 1902. This other John Henry Dittmer was born in Hamburg and lived in Kirkdale.
Deaths Dec 1902   (>99%)
Dittmer  John Henry  51  W. Derby  8b 262

Aged 56 in 1911
Aged 67 in 1911, born Lueneburg, Lower Saxony, Germany.

Probably from Hanover province.

Catharina Mari Dorothea Hoyer was born 21 May 1856 at Gross Klecken, Hannover.  Could this be her?

On her marriage Certificate she is Katharina M M Heuer.

Deaths Mar 1927   (86%)
Dittmer  Catherina M M  73  W. Derby  8b 927

10 Mar 1927, Catherine M M Dittmer, aged 73 of Allon (or Alton) Road, Tuebrook was buried in the Dittmer family grave at Kirkdale.

Private Grave, NC division (section).
Section: 5
Grave: 76

DITTMER, ANNA  MARIE CHRISTINA     HEUER 
GRO Reference: 1875  J Quarter in LIVERPOOL 
Volume 08B  Page 57

Name: Anna M C Dittmer
Birth Date: abt 1876
Date of Registration: Apr-May-Jun 1941
Age at Death: 65
Registration district: Southport
Inferred County: Lancashire
Volume: 8b
Page: 1668

Probate:
DITTMER Anna Marie Christina of 42 Alton-road Tuebrook Liverpool spinster died 14 May 1941 at Southport Convalescent Hospital Leicester-street Southport Lancashire Administration Liverpool 16 July to Charles August Dittmer shipwright. Effects £610 17s 11d.

Headstone reads:
Also Marie, / beloved daughter of the above / who died 14th May 1941, aged 65 years. 

DITTMER, MARGARET  ELIZABETH      HENER 
GRO Reference: 1877  S Quarter in LIVERPOOL 
Volume 08B  Page 17

Deaths Mar 1878   (>99%)
DITTMER  Margaret Elizabeth  0  Liverpool  8b 6

Name:    Margaret Elizabeth Dittmer
Death Date:    13 Jan 1878
Cemetery:    Anfield Cemetery and Crematorium
Burial or Cremation Place:    Anfield, Metropolitan Borough of Liverpool, Merseyside, England
Has Bio?:    N
URL:    https://www.findagrave.com/memorial/174902972/margaret-elizabeth-dittmer

Margaret Elizabeth Dittmer
BIRTH    unknown
DEATH    13 Jan 1878
BURIAL    Anfield Cemetery and Crematorium
Anfield, Metropolitan Borough of Liverpool, Merseyside, England
PLOT    Unconsecrated Sec.4, Grave 845

DITTMER, GEORGE  WILLIAM      HAUER 
GRO Reference: 1878  D Quarter in LIVERPOOL 
Volume 08B  Page 51

George worked at Lever Brothers (now Unilever) at Port Sunlight Soap Works.  He suffered very badly from asthma, possibly caused by his work.  He died before Alice of chest trouble..

He died before Alice, who was Killed in 1940

Probate:

Recorded as aged 36 on 9-Aug-1917

DITTMER, CHRISTOPH  FRIDERICK      HEUER 
GRO Reference: 1881  M Quarter in LIVERPOOL 
Volume 08B  Page 28

Frederick was an Assistant Steward in the merchant marine and served on SS Verdi (Lamport and Holt Line), the vessel plied the Liverpool to New York route, she was torpedoed by U53 in the Atlantic on 22 Aug 1917- the vessel was built in 1907, 7,120 tons deadweight, and sank 115 miles North West by North of Eagle Island, 6 crewmen were lost, she was carrying general cargo when sunk, Christopher Frederick is included in the roll of honour in Liverpool Cathedral and there is a plaque on the Merchant Marine Memorial on Tower Hill.

The Captain of U53 was Hans Rose one of the top 10 U boat aces of WW1, he was responsible for over 200,000 tons of Allied shipping losses during WW1, his boat was surrendered to the French on 11 Nov 1918.  He went on to become one of the main U boat trainers in WW2.

Family stories tell that Frederick was killed trying to save another sailor after being torpedoed.  Just 13 days earlier he had arrived in New York from Buneos Aires, which was recorded and Indexed.

CWGC Reference:
Name: DITTMER, CHRISTOPHER FREDERICK
Initials: C F
Nationality: United Kingdom
Rank: Assistant Steward
Regiment/Service: Mercantile Marine
Unit Text: S.S. "Verdi" (Liverpool)
Age: 36
Date of Death: 22/08/1917
Additional information: Son of Cathaine Maria Margaret Dittmer, and the late John Henry Christopher Dittmer; husband of the late Maud Seymour Dittmer. Born at Liverpool.
Casualty Type: Commonwealth War Dead
Memorial: TOWER HILL MEMORIAL

He is listed on his parents headstone

    
DITTMER, ANNA  ELIZABETH      HEUER 
GRO Reference: 1883  M Quarter in LIVERPOOL 
Volume 08B  Page 4

Val Hawkyeard (RootsWeb) has her as Ann Elizabeth born.1882, so probably born Dec 1882 and registered in 1883. This is consistant with death age 70.

My mother remembers her, so must have died after 1920.

Name: Anna E Walker
Birth Date: abt 1882
Date of Registration: Oct-Nov-Dec 1952
Age at Death: 70
Registration district: Liverpool North
Inferred County: Lancashire
Volume: 10d
Page: 436

Probate:
WALKER Anna Elizabeth of 7 Aslsey-crescent Liverpool 12 widow died 14 December 1952 at Broadgreen Hospital Liverpool 14 Probate Liverpool 2 March to Christopher Dittmer shipwright. Effects £1656 16s 11d

Aged 6 in 1891

DITTMER, WILHELM  HEINRICH      HEUER 
GRO Reference: 1884  D Quarter in LIVERPOOL 
Volume 08B  Page 36

Headstone reads:
William, / drowned 14th Oct. 1919, aged 34 years.

Its not clear where the drowning occured, but possibly local as the war ended November 1818.

There is no UK death record in 1919.  Bremen, Germany and Hannover, Prussia, Germany, Lutheran BMB records have a death record for Carl Heinrich Friedrich Wilhelm Dittmer in 1819, so is this him?

DITTMER, JOHANN  HEINRICH RICKHARD     HENER 
GRO Reference: 1886  D Quarter in LIVERPOOL
Volume 08B  Page 26

My mother doesnt remember Henry, so may have died young (before 1930) or now believed to have emigrated to Australia.

Name:    Henry Dittmer
Birth Date:    1887
Death Date:    12 Jun 1939
Cemetery:    Melbourne General Cemetery
Burial or Cremation Place:    Carlton North, Melbourne City, Victoria, Australia
Has Bio?:    N
URL:    https://www.findagrave.com/memorial/190254332/henry-dittmer

DITTMER, HERMANN  HINRICH CHRISTOPH     HEUER 
GRO Reference: 1889  M Quarter in LIVERPOOL 
Volume 08B  Page 15

DOB 13 Dec 88 recorded on 1939 England census

DOB 9 Dec 1888, born Liverpool on Merchant Seaman record.

My mother remembers Chris, so must have died after about 1930.

Was alive in 1961 when his wife Elizabeth died, leaving him £851.

Name: Christopher Dittmer
Birth Date: abt 1889
Date of Registration: Jan-Feb-Mar 1964
Age at Death: 75
Registration district: Liverpool North, Lancashire
Volume: 10d
Page: 138

Probate:
DITTMER Christopher of 12 Eaton Road North Liverpool 12 died 16 January 1964 as Newsham General Hospital Liverpool 6 Administration Liverpool 18 February to Dora Margaret Latimer married woman. £1610.

DITTMER, JOHN  HERMANN      HENER 
GRO Reference: 1892  D Quarter in WEST DERBY 
Volume 08B  Page 368

Lancashire Birth indexes for the years: 1892
DITTMER    John         Kirkdale    Liverpool    KIRK/81/87

Deaths Jun 1896   (>99%)
Dittmer, John Hermann 
Aged 3
W. Derby  8b 258

Headstone reads:
John, / died 6th June 1896, aged 3 years.

DITTMER, CATHERINE        HENER 
GRO Reference: 1895  M Quarter in WEST DERBY 
Volume 08B  Page 430

Lancashire Birth indexes for the years: 1895
DITTMER    Catherine         Kirkdale    Liverpool    KIRK/93/14

Deaths Mar 1895   (>99%)
Dittmer  Catherine  0  W.Derby  8b 389  

DITTMER, CHARLES  AUGUST      HENER 
GRO Reference: 1896  S Quarter in WEST DERBY 
Volume 08B  Page 376

Lancashire Birth indexes for the years: 1896
DITTMER    Charles A     Kirkdale    Liverpool    KIRK/99/45

Name:    Charles Dittmer
Birth Date:    23 Jun 1896
Date of Registration:    Dec 1970
Age at Death:    74
Registration District:    Liverpool
Inferred County:    Lancashire
Volume:    10d
Page:    989