Merry is a Brandybuck, they were the first ten Thains of the Shire and founded Buckland. He is the only son of the Master of Buckland. Pippin is a Took, they took over as Thains after the Brandybucks left, his father is currently the Thain of the Shire, and his father's sister is Merry's mother. Frodo is a Baggins, no title but wealthy and influential, his mother is Merry's grandfather's sister, and Bilbo' mother is the daughter of Thain Old Took.

And Sam, well, his father is a well respected gardener, and his grandfather was a roper by trade.