So I'm expecting my second baby boy our first is called Noah and we wanna name our second Jackson only trouble is my bestfriends little boy is called Jack there's not really any other names I like and I've loved Jackson for the longest time long before her little one was born and I don't intend on Jackson having Jack as a nickname he'd be Jackson or JJ (his middle name will be James) can I do this? sounds so silly asking but I know how personal some people get over baby names
Jack is a diminutive of John and James is a form of Jacob. They are both Hebrew in origin but not the same name (Jacob means the supplanter where John means god is gracious). Not sure if the meanings are important to the OP anyway - Jackson means son of Jack and she's not mentioned the name of her partner, but I don't suppose he is a Jack.
To answer the OP's question I think if you are planning to call your son JJ then it's not an issue at all.