She has no one left, clearly, if she's living under the care of one of her kids' kids. No husband anymore. All her children were probably killed in a car wreck or sent to jail or something. Way back, it might have been her taking care of you, but she quickly became infirm and helpless. So it came to pass that you started taking care of your grandma and are therefore a good person.
"Wesley?" she shouts downstairs.
You can't answer because you're making meth in the basement, but only to raise some money for an orphanage that's down on its luck.
"Wesley?" she shouts again.
"Coming grandma!" you say. You head upstairs to the kitchen to get her dinner out of the oven. You stop in the living room on your way and you grab a single yellow rose from a vase and place it on her dinner tray. Then you head upstairs.
"Happy birthday Grandma," you say. She smiles a big smile and claps her hands once.
"Such a good grandson," she says. "What would I do without you?"
"Guess you'd have to be the prettiest grandma all by your lonesome, wouldn't you," you say.
Your grandma laughs, then she waits as you spoon her meal into her mouth.
Just then a shady character from your past pulls into the driveway to make you a proposition that will change everything and send you down the road to either redemption or ruin, but you'll be able to reunite with your one true love along the way so that's bitchin'.
"One more bite Grandma?" you ask.
Both of you hear the car door outside.
"You keep quiet, okay grandma?" you say. "I'll go see who it is."
You get up from the bed and close the door. The next time you see your grandmother, you'll be standing over her corpse making her a promise that you're going to get the bastards who did whatever it was they did to turn her into a corpse.
Happy You Are A Good Person Because You Take Care Of Your Grandmother Day!