I'm studying numerals and I found this example: У меня есть 2 старших брата, и одна старшая сестра far as I know after У меня есть It should be an nominative, so for the rule of the numbers the 2 should need the genitive singular (and thats ok cause брата is right) but why the adjective does not respect this rule? It seems to me in plural (Genitive or Accusative). Can you help me?
My understanding of the various facets of the numeral-case system is like this:
1--Both masculine and feminine countable nouns and the adjectives that describe them are in the nominative case. Ex: один чёрный кофе, одна прекрасная принцесcа
2-4 Masculine--Noun is in the genitive singular, adjective in the genitive plural. Ex: два сильных спортсмена, or as in your case: два старших брата
2-4 Feminine--Noun is in the genitive singular, adjective is in the nominative plural. Ex: две сильные спортсменки
5-20--Noun is in the genitive plural, adjective is in the genitive plural Ex: двадцать сумаcшедших людей
Well, it's just like that. You have to remember this.
The long story: here "брата" is actually a relict of dual number, not singular. Some time ago it must be kind of "два старша брата", yet adjectives didn't keep any trace of dual form until nowadays, so for 2..4 it is now like this: "plural adjective" + "singular noun".
Unfortunately I really do not know much English. But the reference to the rules. Maybe someone will be able to translate them. §193. Определение при существительном, зависящем от числительных два, три, четыре