Is dyslexia hereditary? How to identify it at young age?

i think dyslexia is hereditary. my dad has it very mildly but my younger sisters have it. i asked my mum and she said that she knew because they found it really hard to read. they would get letters like b and d misked up and p and q. they would never remember words like the and stuff after reading them. there reading books were much easier than everyone elses in there cl. things like that but my mum made them have extra cles especially for dyslexia and then took them to a dyslexic centre to get tested. now they get a bit of extra time in exams for tests as their reading is quite slow and more help in cl. they were like 4 when my mum noticed something and by 7 they had been tested and everything. good luck