I am currently waiting for my ADHD assessment (next month). I don’t want to ask my family to contribute to my assessment.
First you have a lot of symptoms you identify with so make a list of times from you childhood and now that show how these symptoms affect you.
You are not expected to hit every criteria maybe you are more daydreamy than distracted ADHD is different for everyone.
I am lucky enough to have some of my old school notebooks and reports. If you have anything like that it might be worth going through as it might jog your memory of things that happened or how you thought and felt when you were younger.
Even old photos might remind you of stories people have told you about yourself when you were younger.
You could also try to fish out some information from your sisters without telling them about the assessment. You could just say I feel like I am more daydreamy than I was when I was younger, what do you think?
But don’t stress too much as any competent assessor will know how to assess an adult with limited childhood knowledge and if you disagree with the assessment you can always ask for a second opinion!