Yes. English doesn't distinguish between paternal and maternal grandparents but Swedish does.
Mat. Grandparents = Mormor, Morfar / Morföräldrar
Pat. Grandparents = Farmor, Farfar / Farföräldrar
Great grandparents go like Farfars far and farmors far, farfars farfar and farmors farmor etc.
Children go the same way: Barnbarn, dotterdotter, sonson etc.
So what does "hos" actually mean? Like is it a verb, or is it an adjective? Does it, on its own, mean "at home/at x's place" or is it a case of excluding a preposition for no real reason? Also, why does "oss" come after it here? Why don't we use a possessive pronoun to say whose house in this scenario?
hos is a preposition. There's no real counterpart in English in this case. A grammatically similar construction is with us, but then that would be med oss in Swedish. Rather it's that in English, you have the set expression 'at our place' that you use instead of preposition + pronoun. In French for instance, they have the same construction as we do, they'd say chez nous to express this.