It's probably all a bit overwhelming to get so much information at one time so here's a brief family tree with the details found so far-
John Doak (c1815-aft.1871) m. Elizabeth Hettrick/Hatrick? (c1829 Londonderry?, Ireland-27 Dec.1908)
1861 census- Greenock West: John Doak, 40, mason’s labourer, b.Ire.; Elizabeth Doak, 31, b.Ire.; Robert Doak, 14, b.Ire.; Margaret Doak, 12, b.Glasgow; James Doak, 8, b.Greenock; John Doak, 6, b.Greenock; William Doak, 3, b.Greenock; Samuel McSwean, 1.
1871 census- 108 Drumfrochar Rd., Greenock: John Docks, 56, unemployed labourer, b.Ire.; Elizabeth Docks, 35, b.Ire.; James Docks, 16; John Docks, 15; William Docks, 11; Margaret Docks, 7; David Docks, 7; Joseph Docks, 4. Also 4 boarders named Wilson.
1881 census- 10 Nile St., Greenock Middle (all children b.Greenock): Elizabeth Doak, 45, b.Ire.: William Doak, 25; Margaret Doak, 18; David Doak, 16; Joseph Doak, 14. Also 3 lodgers.
1891 census- 7 Nile St., Greenock West (all b.Greenock unless shown otherwise): Elizabeth Doak, 57, b.Londonderry?, Ire.; David Doak, 26; grandson James Dioak, 9;George Rooney, 23, sailor, b.Belfast; Maggie Rooney, 26; lodger John Doak, 58, b.Arran; lodger Malcolm Livingstone, 5, b.Jura.
Elizabeth Doak died at 82 Drumfrochar Road, Greenock on 27th December 1908 age 79. (Greenock Telegraph 28.12.1908)
1. Robert Doak (c1847 Ire.-aft.1861)
2. Margaret Doak (c1849 Glasgow-aft.1861)
3. James Doak (c1855-aft.1871)
4. John Doak (c1855-22 May 1889) m. Janet
John, son of Elizabeth Doak, died at 7 Nile Street, Greenock on 22nd may 1889 age 34 – wife Janet (Greenock Telegraph 23.5.1889)
5. William Doak (c1860 Greenock-Jan.1911) m. Ann
William Doak, baker, husband of Ann, died at 77 Regent Street, Greenock in January 1911. (Greenock Telegraph 11.1.1911)
6. Margaret Doak (c1862 Greenock-aft.1881)
7. David Doak (c1863-1908) m. Catherine Currie
8. Joseph Doak (c1867 Greenock) m. Margaert Denny
Joseph Doak to Margaret, 2nd daughter of John Denney, joiner, at 34 South Street, Greenock on 6th June 1889. (Greenock Telegraph 7.6.1889)
These may also be connected-
Janet, youngest daughter of James Doak, mason, to Hugh Crawford Small, engineer, at 42 Holmscroft Street, Greenock on 22nd July 1879 by Reverend M. Reid. (Greenock Telegraph 26.7.1879)
A daughter to Mr & Mrs David Doak, engineer, born at 22 Trafalgar Street, Greenock on 26th August 1912. (Greenock Telegraph 26.08.1912)
James Doak, moulder, to Mary Hyndman, youngest daughter of late William McColl, contractor, at Greenock on 25th February 1898. (Greenock Telegraph 02.03.1898)
? William, infant son of James and Elizabeth Doak, died at 15 Regent Street, Greenock on 16th February 1900. (Greenock Telegraph 16.2.1900)
A daughter to Mr & Mrs James Doak, jnr, moulder, born at 4 Prospecthill Street, Greenock on 20th February 1901. (Greenock Telegraph 21.02.1901)
A son to Mr & Mrs James Doak, jnr, moulder, born at 4 Prospecthill Street, Greenock on 13th January 1903. (Greenock Telegraph 13.01.1903)
Jessie Bell, daughter of James Doak, moulder, 31 Dempster Street, to John Thomas Massicks, at 14 Kelly Street, Greenock on 7th June 1912 (Greenock Telegraph 11.6.1912)
James Doak, ironmoulder, died at 31 Dempster Street, Greenock on 5th September 1912 age 70. (Greenock Telegraph 05.09.1912)