ooooh that's a difficult one gemma. If your the mother of the child and your talking about the father then I understand your anger at the cheek of him turning up now after you've done the hard graft.
However, if you put yourself in the childs position, they just want their parent, and they have a right to now. surely its better after 7years than 18years for the reunion.
If the parent is stable (job, life, house, etc) and is serious about getting to know the child then you have to let it happen.
but I am just speculating on your situation. if you give us some more details I'm sure you'll get more indepth advice.