Grany minor Royal means someone not a close blood relation of the monarch: child, grandchild, sibling and occasionally a sibling's children. Roughly within 10 steps of the throne.
Lord Mountbatten does not fall into this group, he is minor royalty, whatever his personal relationship to some of them was.
There is nothing new about Lord Mountbatten's sexual tastes. Both he and his wife had colourful sex lives. All these events happened 50 or more years ago, when, the biggest crime when dealing with behaviour like this was being found out.
The behaviour of Lord Mountbatten and paedophiles in all levels of society at that time, would have been unlikely to have landed him in court.
This behaviour is beyond unacceptable now, we understand the damage it does to children, but we can only judge the past by the standards of the time.
By the way did you know that Joan of Arc was a close associate of a man now described as the first 'serial killer'. Gilles de Rais, He is said to have abducted, abused and then killed as many as 200 young boys. I think we should 'cancel' Joan of Arc because she must have known, mustn't she something about his terrible behaviour.
Just how far back do we go in raking up past behaviour that would quite rightly be shocking now, but at the time was seen as acceptable.