I have a lot of brothers or I have a lot of siblings.
You have brothers or sisters.
If you have brothers or sisters or both, you say, "Sí." Then you say how many of each you have: Tengo ______ hermano/s. (for brothers) Tengo ______ hermana/s. (for sisters) Tengo ______ hermano/s y _______ hermana/s. (for both) If you are an only child, you answer, "No; no tengo hermanos."
I'm very nervous.
Tengo muchos amigos
I have siblings.
To say I have a sister and two brothers in Spanish, you would say: Tengo una hermana y dos hermanos
Tengo tres hermanos
If what you mean to say is "I have one brother," the words in Spanish are, "Tengo un hermano." It is pronounced "TANE-go oon air-MAH-no." See the related link for audio pronunciations of many common Spanish words.
Translation: Tengo dos hermanos
Tengo muchos caballos y perros.
"Tengo muchos libros para leer."
Literally, on its face, it means, "How many brothers do you have?" But implicit in the word hermanos (and the question itself) is the word hermanas. So what the question is really asking is, "How many brothers and sisters do you have?" An answer revealing the number of sisters in one's family as well as brothers would not be unexpected. In Spanish questions, there is usually an accent on the adverbial question word; in this case, ¿cuántos?
Tengo tres hermanas y tres hermanos