Could be a timing thing, did you very recently sign the honor code? Even though I see the badge on your profile I think the system can take up to 24 hours to catch up.
I also seem to recall (but could be mistaken) that as a newt you can create your own profiles and edit them but until you have made about 100 contributions you wont be able to edit other profiles.
Check this article out to make sure you are following the right process to add family, if you are and it wont let you it could be what I suggested above. In that case you can ask for someone to do the add. Happy to help if you need it. https://www.wikitree.com/wiki/Help:Editing_Family_Relationships