I have written a memoir through a workshop taught by a known writer. A friend now in book publishing made a mock up prototype and added my pictures without my knowledge - I loved it - what legal obligation do I have to those seen in those pictures living and dead?
It depends where the photo was taken. What the photo is being used for. And whether any minors are in the photo.
If the person or subject of the photo is who you are writing about, you will probably need a release. There are a few exceptions, such as a public figure, and/or editorials.
I took a photo in a crowded public park to capture a certain person of interest. The article which accompanied the photo focused on this single individual. Had this person been wearing normal clothing, I would have needed a 'release' to use their image in the manner in which it was used. However, because they were dressed in what could be determined a costume, and their goal was to garner the attention of the public, this made them the equivalent of a public figure. So I could do what I did without obtaining a release. But there was one caveat. A minor was also in the un-cropped image and had to be photo-shopped out of the image before the publication could be re-released. I chose to use a close-up instead, and many faces were recognizable, but the photo was taken in a public place, and no attention brought to them.
Since you are writing a memoir, are you bringing attention to certain individuals in the photo? Was the photo taken in a public place or in a private home or private gathering? If in private, then the people in the image have a right to their privacy and you will need a release from those living, also from the family of those deceased. Unless your memoir is presented only to family members as a private publication.
I am not an attorney, and this is not to be considered legal advice.