can a girl listen to men singing Islamic nasheeds?can she wear pants in front of her brothers?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
There is no harm for a woman to wear pants in front of her brothers provided they are not transparent and do not show the form of her limbs. However, it is a condition that the pants do not resemble men’s or non-Muslims' pants.

As for listening to the Anasheed (Islaamic songs without music) sung by men, then it is permissible for her to do so. Anjashah used to sing the camel-chant while women were riding on these camels, and he had a nice voice; this is narrated in a Hadeeth reported by Al-Bukhaari and Muslim.

Allah knows best.