I believe I can clear up some confusion about this man's birth and siblings--a family that moved from Cornwall to Ishpeming, Marquette, MI.

The 1910 census, Ishpeming MI, lists him as Henry COWLING, age 40, miner of iron ore, born in England,wife Esther. In his household is listed Susan, mother, age 66, born in England, and also his brother Charles, age 39.

The 1900 census, Ishpeming, lists him as William H. COWLING, age 30, born Nov 1869, England, wife Esther. Above him on the same census page is a listing for Susan COLLING, head, widow, age 56, born Mar 184? in England--7 of her 10 children were living in 1900. In her household were son Charlie 26, daughter Emily 19, and son John 16. All were born in England, immigrated 1900. [Notice that their father was dead by 1900.]

The census reports for 1920 and 1930 list unmarried brothers Charles and John in the household of William H. COWLING, Ishpeming.

Looking at the census reports from Cornwall for William COWLING/COWLIN and Susan, one can draw up a list of their children:
Jane c1867,
William H and Lewis (twins)c1869,
Charles c1872,
George c1875,
Emily c1881, and
John c1883.
This family matches with the two households in Ishpeming. Willima Henry's twin Lewis was also in Ishpeming in 1900, 1910, and 1920.

The 1871 census lists the age of the twins as 2 years.

William Henry COWLING and Louis (Lewis) COWLING were christened 3 Jan 1869 in St. Gerrans, sons of William COWLING and Susan--from parish records as seen on IGI, www.familysearch.org. They appear on the December quarter of birth registrations for 1868, Truro district, on FreeBMD. While their ages seem to vary inconsistently from year to year on the records, they must have been born in Nov. 1868.

The following posting of marriages in the parish of Gerrans, Cornwall, indicates that William COWLING, labourer and widower age 35, son of Samuel COWLING (farmer), married on Dec 25 1867 in Gerrans to Susan EBBETT, spinster age 26, daughter of William EBBETT (Coast Guardsman).

http://www.rootsweb.com/~enggerop/marriages_post1837B.htm

Susanna Rebecca EBBETT was the daughter of William Wilkins EBBETT, Coast Gaurdsman, and his first wife Sarah Maria (nee BEST, to the best of our knowledge). She was born Mar 18, 1842 (from family records) and christened 8 May 1842, according to parish records for St. Agnes near Truro as seen on the IGI at www.familysearch.org, daughter of William and Sarah Maria IBBELL (that must have been read from a faded page.)

On the 1871 census, you can see her in Gerrans as Susan COWLIN age 29 born St. Agnes, the wife of William COWLIN, agr. lab. age 40 born Wadebridge, along with the two twins, William and Lewis age 2 born in Gerrans. The Jane E. listed is not a child from this marriage. I will post a note about her under her own name, Jane EBBETT [1867].

Tying it all together, the 1881 census lists the family as William COWLING 50, Susannah 38 (St. Agnes), William H. 13, Lewis 13, Charles 9, and George 6, and in 1891 as William and Susan COWLIN, they have Emily 10 and John 8.

Emily married Richard SMITH, 10 Feb 1906, Silver Bow Montana (from IGI). I do not know what happened to George.