Here is some information on Kaighins who served in the American Civil War:

Name: Charles Kaighen ,
Enlistment Date: 20 April 1861
Distinguished Service: DISTINGUISHED SERVICE
Side Served: Union
State Served: New York
Unit Numbers: 1379 1379
Service Record: Enlisted as a Private on 20 April 1861 at the age of 25
Enlisted in Company I, 11th Infantry Regiment New York on 07 May 1861.
Mustered out Company I, 11th Infantry Regiment New York on 02 June 1862 in New York, NY

I believe this is the same Charles Kaighin:

Name: Charles H Kaighen ,
Enlistment Date: 11 August 1862
Distinguished Service: DISTINGUISHED SERVICE
Side Served: Union
State Served: New York
Unit Numbers: 1442 1442
Service Record: Enlisted as a Private on 11 August 1862 at the age of 27 Enlisted in company G, 170th Infantry Regiment New York on 07 October 1862.
Deserted Company G, 170th Infantry Regiment New York on 12 October 1862 in Staten Island, NY

John Kaighin, wife Mary A. Kaighin, filed a Civil War Pension Card in California 1902 Oct 1, and she became a widow 1913 Oct 30. He served in Union 58th NY National Guard, and 56th NY National Guard. Enlisted and discharged as a private.

From a Civil War pension card:
Kaighin, James A., 1599 E. 86th St. Cleveland Ohio, R14292

The following records are brothers, George P. and Charles E. Kaighin of Cleveland, Ohio. Charles died in January of 1865 from wounds received in battle. They are the sons of William Kaighin and Mary ____. George was born about 1845 in Brooklyn, NY, and Charles was born about 1846 in Brooklyn, NY. Their father William was Christened 21 Dec 1803 in K. Michael, the son of John Kaighin and Eleanor Cannell.

From Cuhahoga County Military Roll of Honor, Infantry:
Kaighin, Charles E.
Rank: Private
Unit: 150th
Company: B
Record: 701

Kaighin, George P.
Rank: Corporal
Unit: 150th
Company: B
Record: 700

From American Civil War Soldiers

George Kaighin
Enlistment Date: 05 May 1864
Distinguished Service
Side Served: Union
State Served: Ohio
Unit Numbers 1782
Service Record: Enlisted as a Corporal on 05 May 1864 at age of 19 (born about 1845) Enlisted in Company B, 150th Infantry regiment Ohio. Mustered out of Company B. 150th Infantry Regiment Ohio on 23 August 1864 in Cleveland, Ohio. Pension filed by widow Olive M. Kaighin 13 Dec 1895 in the state of Missouri,

Charles Kaighin
Enlistment Date: 05 May 1864
Distinguished Service
Side Served: Union
State Served: Ohio
Unit numbers 1782
Service Record: Enlisted as a Private on 05 May 1864 at age of 18 (born about 1846)Enlisted in Company B, 150th Infantry Regiment, Ohio. Mustered out on 23 August 1864 in Cleveland, Ohio.