Have you treid "i'd love to mom, but grandpa bought those, i'm just taking care of them, so we better check with his first".
He's most liekly thrilled that you're into fowl when most kids your age can't tell a duck from a goose. Grandparents are funny,the sometimes forget there's other parents involed, he may be thinking "it's fine to get ducky more chickens, that's engouraging him in his passions, i'm sure his parents won't mind". My guess is he knows he's getting old, and would like to keep a farmer in the family.
He's most liekly thrilled that you're into fowl when most kids your age can't tell a duck from a goose. Grandparents are funny,the sometimes forget there's other parents involed, he may be thinking "it's fine to get ducky more chickens, that's engouraging him in his passions, i'm sure his parents won't mind". My guess is he knows he's getting old, and would like to keep a farmer in the family.