No you're reason is not good enough

Basically you are saying

"I want to visit my grandma and my excuse is because I haven't seen her in 15 years"

1. Work Purposes
2. Humanitarian reasons (visiting someone does not fall under this reason unless shes half dead, you can medically prove shes about to die or die while you were there)
3. School/education purposes


Does this fall into any of these?