How certain are you that Benjamin's mother's name was Mary?
There's a death record for a Benjiman Franklin ALSOBROOK b. 11-Mar-1865 in AR, d. 30-May-1931 in Colorado, Mitchell Co, TX.Parents are listed as David ALSOBROOK and Nancy GOZY.Benjamin's wife is listed as Mary E. ALSOBROOK.
The 1880 census for Princeton, Dallas Co, AR: ALSOBROOK, David age 61 b. NC, both parents b. NC wife Nancy E. age 41 b. AL, both parents b. NC dau Isabella age 27 son Robert age 25 son David L. age 23 son Benjamin F. age 14 son Jasper S. age 10 dau Manurva age 7 son John L. age 3
All the children were born in AR.
There's a marriage record for a David ALSABROOKS, age 43, to Nancy WARD, age 21, on 3-Jan-1861 in Dallas Co, AR.
It's possible that Nancy was a widow or divorced at the time of her marriage to David because I found a marriage record for a Nancy E. GOZA to John B. WARD on 20-Nov-1856 in Union Co, AR.
In 1870, same location: ALSOBROOKS, David age 50 b. NC Nancy E. age 30 b. AL Della age 19 b. NC Isabella age 17 b. AR Robert age 13 b. AR David L. age 11 b. AR Benjamin age 4 b. AR Samuel G. age 2 b. AR
In 1860, same location: ALSABROOK, David age 40 b. NC Kelm age 10 b. NC Adaline age 8 b. TN Isabella age 6 b. AR Robt. age 5 b. AR David age 3 b. AR
The 1850 census for Edgecombe Co, NC: ALSBROOK, David age 30 b. NC Mary P. age 25 b. NC Kenelum age 1 b. NC