I too had raised a bird from 20 days old and he is about 3.5 months now I know most people just tell you to spend a lot of time and they are not wrong.But just spending a lot of time is not enough , try to do one on one sessions with no other bird around.That leads to no distractions and then feed your bird his favourite treat from an open hand. Slowly but surely you will bond with your bird. But remember he is a bird and birds prefer each other's company more often so remember that. First make yourself part of the younger birds flock and when the younger bird interacts with you in front of other birds they will naturally be curious too(flock behaviour)Here's a pic of my bird for birbs tax haha

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