I don't think underwear should be given. If you think it's good, I suggest you buy two sets of thermal underwear, which are comfortable. Old people must be comfortable.

As for the saying, there is no such thing as giving gifts out of filial piety. There is no such thing as a statement.

But I still suggest not underwear. It can be clothes, food or decorations. If old people like flowers, I'm sure your grandmother likes flowers, too. You can buy some potted flowers to make the old people feel better. My grandmother likes flowers, such as Phalaenopsis, bergamot and rhododendron. . . . . . . . . . . . .

No matter what you buy, it is your filial piety. I wish your grandparents good health here!