Learn Italian: Il nonno sta in piedi vicino alla finestra. - Grandpa is standing near the window.

Italian doesn't have a single verb that means "to stand." Instead, it uses the phrase stare in piedi, which literally means "to stay on feet." To say someone is standing, you simply use the present tense of stare with in piedi.

Could I say è in piedi instead of sta in piedi?

Yes, you can! Both è in piedi and sta in piedi are completely natural and mean "he is standing." While stare is often used to describe body postures, essere works just as well here.

Why is it vicino alla finestra and not just vicino la finestra?

When the word vicino (near) is followed by a noun, it must be paired with the preposition a (to). Because finestra is a feminine noun that uses the article la, you combine a + la to make the combined word alla.

If there were multiple people standing, would in piedi change?

No, it wouldn't change. Piedi is already the plural form of piede (foot). Whether it is one grandpa or two grandparents, they are always standing in piedi.