[Maximo]

Do you share a home with your grandson or is this happening during visits?

I would start with making sure Charlie gets plenty of exercise. Work on obedience/trick training with him too. Have yummy treats for when your grandson is around and reward Charlie for when he behaves.

If your grandson is visiting, take Charlie out for a walk first, or do something special with him. When your grandson arrives, make Charlie sit and perform other tricks for treats. Try not to show anger or frustration when correcting Charlie or he will associate your grandson with everything bad.

Trainer Victoria Stilwell has videos and books with more suggestions.

Finally, exercise extreme caution with Charlie around your grandkids. If all else fails, exercise Charlie before visits from family, and then pen him or put him in a room with a comfy bed and toys.