The Martins are the town grocers.  While everyone else avoids the lottery, they seem to want to be involved in it.  They even keep the box in their store sometimes.  This demonstrates that not everyone is afraid of the lottery and some people even like it.  The town could not keep a tradition like this without some people like that. 

Little Bobby Martin seems to really like the lottery.  His behavior borders on sociopathic, because he gets way too much pleasure out of the lottery.  Either that, or he is too young to fully grasp the significance what is going on.  He is the first one to gather the stones. 

Bobby Martin had already stuffed his pockets full of stones, and the other boys soon followed his example, selecting the smoothest and roundest stones…

He also runs around giggling before the lottery starts, until his father speaks sharply to him, aware that his son is being inappropriate.  The Martins keep their enthusiasm for the lottery maintained.  The villagers “kept their distance” from Mr. Summers and the paraphernalia of the lottery when it was first starting.  When Mr. Summers asks for help, most of them stand back.  Mr. Martin, like his son, is right in the thick of it.  He volunteers, along with his other son.

[When] Mr. Summers said, "Some of you fellows want to give me a hand?" there was a hesitation before two men. Mr. Martin and his oldest son, Baxter. came forward to hold the box steady on the stool while Mr. Summers stirred up the papers inside it. 

While everyone else avoids the lottery, Mr. Martin and his son are willing to hold the box while the lottery takes place.  They chat with Mr. Summers during the proceedings.  These things, little the littlest Martin gleefully collecting stones and running around giggling, show that the Martins enjoy the lottery and have a different perspective than the rest of the town.  The apple doesn’t fall far from the tree.  Mr. Martin’s behavior and attitude influenced his sons’.