My brother met with an accident and is in hospital.

Answer

If your intention was good, then it was permissible to have checked your brother's phone. You should delete the filth, and if necessary destroy the device. It is necessary to offer your brother naseehat.

Tell him that in all probability the accident is a mild punishment for the filthy sins he commits via the cellphone. He should make Taubah and Istighfaar in abundance for ruining his Imaan in such a despicable manner. Do not be concerned about him being annoyed. Be concerned with the Pleasure and Displeasure of Allah Ta'ala. It is your duty to offer naseehat to your brother.