First thing first, I'm sorry to hear about your loss.
Frankly, without knowing passcode, it's not possible to access the device and any content that is saved on it directly. iPhone's security isn't something that can be bypassed to retrieve the data from it.
Note that many apps used on iPhone, store their content on the server and information from it is synced to the iPhone. This for instance is for any iCloud service that was enabled on the device; like Contacts, Calendars, Photos, Mail, iCloud Drive, etc.
Apple might be able to help you remove the activation lock and possibly grant access to your brother's iCloud account. There is however certain documentation require to be provided and process normally takes some time too. Contact AppleCare for more details and what documents you'll need to present to them.