I’m mystified that you would allow precious irreplaceable items to be kept or destroyed by a vindictive person.
Sometimes the only way to fight crazy is with crazy.
Sometimes, items are destroyed by a crazy person--in my case, a literal crazy person--my mom. She wasn't mean or vindictive, she was mentally ill. She left our photo albums in a bookcase thing. Outside on her deck. All winter. In Connecticut. We had one (one!) nice, framed photo of my dad's family when he was a child--this photo had hung in my grandmother's house my entire childhood. My mother threw it in the dumpster. My sister literally had to dumpster-dive to retrieve it. I have very, very few photos from my childhood. Does it suck? You bet! But that still doesn't give me the right to break the law! I'm also not mad at my mom--I'm sad. Sad that she couldn't function as a healthy person in this world.
As it happens, I have a quasi-uncle (long story) who's been mentally ill all his life. He's lived in a nursing home for 20 years, and is 79 now. He mailed me several photos from decades ago, including an 8"x10" from my parents' wedding, and another that might be my mom's college graduation. I cried when I saw them--those photos mean the world to me. I GET the importance of photos.
The problem you have is two-fold. One is, you have no right to any photos not explicitly left to you. None, zero, zip. No matter how justified you might feel, you just don't. The other problem is, if you were dealing with a mad, vindictive person, you would only incite them. If it were me, and I was the spiteful type, I would burn that pile of photos after your first attempt to take them--then you would have nothing. A better approach would be to use every ounce of kindness you have, to try to get them to give you the photos. Better yet--if you know your parents have photos that you want copies of, ask now. Offer to sort through them, ask questions, maybe make a nice album or two (one for you, one for the parents).
P.S. If you're breaking in to someone's house to retrieve photos and a recipe box, good luck convincing the judge that THEY'RE the crazy one!