Do I tell my parent that my other parent is cheating?

I am going to add as much context as I can without ranting unnecessarily. A few weeks ago I found out one of my parents was cheating on the other because they have 2 Facebook accounts and I guess they forgot they had me added on both of them. On one they post normal things and it turns out the other is a burner where they speak to their side. I only realized by looking at the comments and originally thought it was a catfish trying to scam my parent (happened once already) but I looked closer and found out the city/country they live in and actually logged into our phone provider to find logs from that exact city and country. The reason I am reluctant to say anything is because my SO told me it’s not my business and to keep my mouth shut but also this happened before years ago when I was a kid and my parents basically fought and then agreed to forget about it. I am also worried for my 3 siblings who still live with them and am unsure how they would handle this. I have been stressing out more than I normally do since I’ve found out to the point my hair loss is getting worse. I guess I am asking what someone else would do in this situation or if anyone has actually gone through this and has advice on how they handled it?