Like dpaterso said, No, none of it is right.
The Brown family and the Vincente family are quite straightforward.
Don't use an apostrophe to make a plural:
- The Browns stood by the fence.
- The Vincentes stood by the fence.
The possessive of a plural adds an apostrophe after the S:
- The Browns' car.
- The Vincentes' car.
The possessive of the singular adds an apostrophe and an S:
- David Brown's car.
- Sarah Vincente's car.
The Jenkins family is a little different. When a proper name (just like any noun) ends with
s, sh, ch, x, or
z:
Plurals: Use
es to form the plural
- The Jenkinses stood by the fence.
Possessives: There are several schools of thought. Pick one and be consistent. Even if an editor disagrees with your choice, s/he will recognize it as one of the standard variations. (In other words, you won't look stupid.)
Plural Possessives:
- The Jenkins' car.
- The Jenkinses' car.
Singular Possessives:
- Carl Jenkins' car.
- Carl Jenkins's car.
- Bob Jones's truck, but Carl Jenkins' car. (some say it depends on the number of syllables--one vs more than one; others say it depends on how it's pronounced)
- Moses' beard, but James's hair (some say Moses, Jesus and a few other "ancient" names enjoy a special status; others say it's because the last syllable begins with s)