I do not remember at the moment, the source for the father/son connection for John and Sewell. Sewell's brother Loyalis my great, great grandfather. In 1849 these brothers lived in Lacon, Marshall Co., Illinois. Here are what I got from the records there:
Land Record in Lacon, Marshall Co., Illinoes Courthouse for Abbot, Book F, page 157 & 158, Sewall A. Abbott bought a house in Lacon, Marshall Co., Illinois on Nov. 29, 1849 from Benjamine C. Crawford for $44. The house is directly East of the house of A.L. McKinney. The house had been built by Sewall. Sewall Sold a horse to Jere"ah Bonham on Feb 4, 1850 for $35.
Here are some other facts that I found about Sewell
!BIRTH: age 24 on 1850 Census Marshall County Illinois. This makes his birth year as 1826. However it may be 1827 (see Civil war info). !BIRTHPLACE: on 1850 Census Marshall County Illinois listed as Pendelton, !CIVIL WAR: Enlisted 29 Dec 1863 at Vinton, Benton Co., Iowa at the age of 36 ( this makes his birth year as 1827). He served in the13th Iowa Infantry, Company A. Discharged for a disability 27 Jun 1865 in Louisville, KY. !RESIDENCE: Native of Pendleton, Niagara, New York (Pendleton is cent ral town !OCCUPATION: Farmer in 1890. !DISCRIPTION: From Civil War records, age 61 in 1890 , 51/2 feet, light