Hey, sorry for your loss. However, don't be frustrated. If you have an iTunes/iCloud backup file for those photos, They can be restored from backups. According to the instructions of Apple, you can try the following steps to retrieve them.
iTunes: Plug in iPhone to connect with iTunes.(Make sure iTunes is updated to the latest version) Head to "File" > "Devices" > "Restore from Backup". Then, choose a previous backup and click on "Restore". Wait till its done.
iCloud: Log in iCloud account on iCloud.com and check out whether the photos are stored here. If so, you might need to reset your iPhone in order to restore them from iCloud. On iPhone go to "Settings" > "General" > "Reset" > "Erase All Content and Settings". Then. after the iPhone reboots, choose "Restore from iCloud Backup".
However, if you don't want to erase your iPhone, try iPhone Data Recovery on iFoneTips. I've got my deleted photos back on iPhone 6s thanks to it. It can even restore without backups. Hope it helps.