For questions about using two different possessive markers, like “of Bob’s” or “of mine”. Also known as 'double genitives' or 'oblique genitives'.

The double genitive is the peculiarly English combination where two different possessive markers are employed simultaneously. This occurs when an inflectional genitive serves as the object of the periphrastic genitive. Historically, this construction is sometimes called the cumulative genitive, the pleonastic genitive, or the double possessive.

To form a double genitive, two different kinds of possessive are required:

  1. These are inflectional genitives (that is, ones marked by case):

    • possessive pronouns: mine, thine, his, hers, its, ours, yours, theirs
    • possessive nouns: Sam’s, Alice’s, James’s, Italy’s, the town’s, the queen’s, my friends’
    • possessive noun phrases marked with the Saxon genitive: the Queen of England’s

  2. These are periphrastic genitives (that is, formed using the preposition of):

    • of Italy, of Sam
    • of the town
    • of me, of us, of them

  3. And these are double genitives, which combine both types of possessive:

    • a friend of Sam’s
    • a friend of ours

This produces opposing pairs of contrasting meaning, the simple form first and then the doubled form second with further added nuance of ownership:

  • a picture of me   vs.   a picture of mine
  • a picture of Sam   vs.   a picture of Sam’s
  • a picture of the town   vs.   a picture of the town’s

In the first of each pair above, the painting depicts a person or a town, whereas in the second, the painting is actually owned by a person or a town and says nothing about the subject depicted.

The OED has an 1898 citation that observes that this construction may be a partitive one:

  • 1898 H. Sweet New Eng. Gram. II. 54

    The pleonastic genitive, as in he is a friend of my brother’s, is generally partitive = ‘one of the friends of my brother’.

Although it has been occasionally frowned upon as inelegant, the double genitive has a very long history in English, and it remains a perfectly normal English construction in good standing.