From SSDI (Soc Sec Dth Idx):
Pupkin, Alex, b 21 Jul 1903; d Jan 1972; last residence Green Cove Springs, Clay Co, FL; SS card issued in VA.
You can visit this site, order a copy of the application he filled out to obtain his Soc Sec card.It should show the names of his parents, his place of residence at the time he applied and other data.
Since the name is so unusal I tried some census records.This is not proof, but sure looks good.
1910 census St Louis Co, MO:
Pupkin, Esidor, h, 51, M(1) 16 yrs, b Ger, Ger, Ger
" Annie, w, 48, M(1) 26 yrs, 10 ch, 7 lvg, b Ger, Ger, Ger
" Benjamin, s, 26, b TN
" B_____, d, 20, b TN
" Helen, d, 18, b TN
" Milton, s, 15, b TN
" Corinne, d, 12, b TN
" Joe, s, 6, b TN
" Alex, s, 6, b TN (twins ?)
[Esidor owns home free and clear, is a merchant, retail dry goods, came to U.S. 1882 & Naturalized.Annie came in 1883]
1900 census Lauderdale Co, TN:
Pupkin, Esadore, h, b Jan 1859, 41, M 17 yrs, b Poland/Russ, P/R, P/R
" Annie, w, b Apr 1863, 37, M 17 yrs, 8 ch, 5 lvg, b Poland/Russ, P/R, P/R
" Benjamin, s, b Sep 1884, 15, b TN
" Bessie, d, b Jun 1889, 10, b TN
" Hellen(sic), d, b Aug 1891, 8, b TN
" Milton, s, b Jan 1895, 5, b TN
' Crinie, d, b Jan 1898, 2, b TN
Tyers, Addie, servant (blk), b Dec 1875, 24, cook
[Edsadore is merchant, dry goods, owns home free and clear.Came to U.S. 1880, been here for 20 years.]
Also in same county is a Rosa Pupkin, b Poland/Russ, P/R, P/R maybe a sister to Esadore?She is sis-in-law to Leopold Berkowitz, I cannot read his wife's name, but she also is born Poland/Russ, P/R, P/R, it says she came to U.S. 1898, but it probably was meant to be for her husband.Two daus 8 and 2 born same location as father, then son 1, b TN.All very hard to read, you might want to check it out.
1920 census Cameron Co, TX:
Pupkin, Esidor, h, 63, md, b Russ, Russ, Russ
" Annie, w, 58, md, b Russ, Russ, Russ
" Ben, s, 35, sgl, b TN
" Milton, s, 25, sgl, b TN
" Corrine, d, 21, sgl, b TN
" Joe, s, 16, b TN
" Alec(sic), s, 16, b TN
[Esidor is merchant, dry goods.Both he and wife listed as coming to U.S. 1883 and both naturalized 1890 -- you might check in TN for naturalization record.]
In the same county looks like Ben moved out on his own and was counted twice, he is living in a boarding house, and mother tongue of his parents is listed Yidish.
1930 census Cameron Co, TX:
Wunderman, Chas. M., h, 43, m @ 27 yrs of age, b Minn, Romania?, Romania
" Bessie, w, 39, m @ 23 yrs of age, b TN, Russ, Russ
" Dan, s, 12, b TX
Pupkin, Milton, b-in-l, 33, b TN, Russ, Russ
" Ben, b-in-l, 44, b TN
" Alexander, 24, b TN
[Chas is an attorney, law office, 3 Pupkins are salemen]
Maybe Bessie is the sister in TX you mentioned. Here's hoping this is the correct family.
Happy Hunting (^_^)