My grandparents have 2 t5’s under a joint bank account, but only my grandfather’s SIN (Canada) is listed.

Canadian Tax:
Both their names are on the T5 but only my Grandfather’s SIN. Before I realized that, I tried claiming the income (just shy of $17,000 CDN) for one then the other and they would collectively owe less money if it was claimed under my grandmother. 

Will the government penalize them if my grandmother claims it instead of my grandfather?

Will they get in