Ok, so my fiance has a child from a previous relationship. The kid has been through a lot and is in the temporary custody of his paternal grndmother. Here's the problem - he was given a name at birth and most people call him by this name. However, his other family has decided to rename him and will only refer to him as this ither name that isnt his own. Also, he calls the grandma and her sister both "mom" and no one corrects him - is only three. Is this ok? Is it going to screw him up?
I don't think that it will mess him up in any way. For him right now his grandma really is the closest thing to his mom (role wise) and it sounds like his aunt is too. As he gets older his constructs of what he sees around him will change he'll begun to understand the difference between moms, aunts, grandmas, and really nice ladies that babysit you for the day, but it takes some kids longer and out sounds like he ready hasn't had much opportunity to see stable family relationships, so it may take him longer than most kids to learn how to separate the different titles from his caregivers that are performing what he sees as "mom" roles.
As far as the new nick name, I would look at it just like that, a new nick name. My almost three year old and my 14m old reach have different nick names given them from different family sides, and my toddler moves between each no problem.