It seems that Gabriel's son and grandson used the surname "Reib," which would mean that Gabriel was a relative of Max Reib Rubenstein, not Fannie Rubenstein.

Arrived 1882. Naturalized in Muscatine, Iowa on October 12, 1888. This means that "G. Rubenstein" who worked for Max Bieber & Co. in Muscatine was probably the same as Gabriel Rubenstein of Alton.

Gabriel Rubenstein appears to have been in business with Max Reib Rubenstein in Muscatine. Since Rubenstein was Fannie's name, he may have been Fannie's cousin or brother. Note the name Dora and Samuel. Dora (Dvora / Deborah) is the name of Max and Fanny's daughter also. And Samuel may be a Reib or Rubenstein family name, according to Sandy Besser.

From 1910, Madison County IL, Alton Ward 2,

• Gabriel RUBENSTEIN 44, RUS-RUS-RUS, Merchant - Clothing
• Rosie RUBENSTEIN 37, RUS-RUS-RUS,
• Dora RUBENSTEIN 14, MO-RUS-RUS,
• Samuel RUBENSTEIN 12, MO-RUS-RUS,
• Nona RUBENSTEIN 8, IL-RUS-RUS,

This means that Gabriel was born in 1866, which makes him slightly younger than Max or Fannie. Rosie in 1871, Dora in 1896 and Samuel in 1898.

Fannie's father's name was given as Nathan Rubenstein on her death certificate, which if true means none of the children were named for her father.

Looks like Max and his (hypothesized) brother-in-law had something in common (the family business?)

Illinois Deaths

• Name: Gabriel Rubenstein
• Birth Date: abt 1864
• Birth Place: Russia
• Death Date: 8 Nov 1928
• Death Place: West Frankfort, Franklin, Illinois
• Burial Date: 10 Nov 1928
• Burial Place: St. Louis, St. Louis, MO
• Death Age: 64
• Occupation: Merchant
• Race: White
• Marital Status: M
• Gender: Male
• Spouse Name: Rose Rubenstein
• Comments: Length of residence where death occurred 11y
• FHL Film Number: 1642729

1900 US Census:

• Name: Gabel Rubenstein
• Birthplace: Russia
• Home in 1900: Belleville Ward 6, St Clair, Illinois
• [St. Clair]
• Race: White
• Gender: Male
• Immigration Year: 1882
• Relation to Head of House: Head
• Marital Status: Married
• Spouse's Name: Rose Rubenstein
• Marriage Year: 1890
• Years Married: 10
• Father's Birthplace: Russia
• Mother's Birthplace: Russia