We had all the censuses for Jennie except 1870 and 1900 but those don't seem to be relevant to the WEST question. She died in 1938 in Oregon so won't be on the 1940.
Alexander and Pheba are parents of Anna WEST who married William McPHEETERS, another collateral relative whose family came from Hawkins County, Tennessee along with the SCISMs, REAs, REYNOLDS's, and others. They are listed on Anna's death certificate and also in a SCISM family history written by DeLos SCISM in 1942.
Anna is the right age (born 1868) to be a younger sister of David WEST. There is a couple that appears to be Alex and Pheba/Phebe on the 1880 census in Kentucky. They have a daughter Mary A. of the right age to be Anna. Like David, she was born in Illinois, as was everyone else in the family. (Alexander and Pheba's birthplaces are not on Anna's death certificate).
David is not on the 1880 census with them but he would have been 22 then and was likely on his own.
Anna and husband William McPHEETERS died in Poplar Bluff, MO, to which a lot of folks from Stoddard County have ties.