Do I tell family history truths that will hurt my dad’s memory?

Warning: this post contains possible upsetting details.
I am 68 with 3 younger brothers but I am only close to the middle one as the others estranged me and my family before my mum’s funeral in 2013. My dad died in 2006 leaving a family in disorder due to his disruptive relationships with each of his 7 children in 2 marriages.
I have written up my dad’s parents family histories so my brother has their life stories and now in lockdown I am writing my dad’s life story. In the 1960’s he had a close friendship with a work colleague, a man who inveigled his way into our home and ‘groomed’ me from 10yrs old then sexually assaulted me in my bedroom several times when I was 12-13yrs old. I reported it to my mum eventually who stopped him coming to our house. She didn’t want to report it to the Police because of the implications of court etc. I learnt later that he was convicted of Paedophilia and jailed. When I was 18 yrs old I unexpectedly met him again at my dad’s works Xmas party: they had stayed friends and dad had given him a job after prison. I was shocked and upset, blocking it all out for many years. I never told my late husband and it was never discussed in the family or with my parents. It has affected my sexual relationships and how I feel about sex. I have some traumatic memories so certain songs and places can reactivate those bad memories. In retrospect I should have had counselling but this was late 1960’s.
So.... do I write up the truth for my brother to read, about my dad’s close relationship with this Paedophile and how he continued with it even after his conviction? My dad may have seen his post prison help as part of resettlement. Will revealing it all now change my good relationship with my brother or is it better to leave it out? As a victim I want to write it into the history but as a sister I want to protect my brother from more hurt and upset.