This is the 6113th most frequent Russian word.
старшего
The Russian word "старшего" means "senior" or "older" (genitive or accusative singular form of "старший").
In this sentence, 'старшего' is used as an adjective in the genitive case, modifying 'брата', indicating 'elder' brother.
Он всегда слушает старшего брата.
He always listens to his elder brother.
Here, 'старшего' serves as an adjective in the genitive case, describing 'поколения', referring to 'elder' generation.
Мы пошли за советом к старшего поколения.
We went for advice to the elder generation.
The word 'старшего' functions as an adjective in the genitive case modifying 'школьника', meaning 'elder' schoolchild.