Be careful with the metal/plastic in the clothes pegs if the metal becomes rusty or the plastic has certain colourings it can be toxic to your bird. Your best to use stainless steel millet clips for this instead of clothes pegs. You can double it up by hanging fresh leaves from them for your birds to eat

He's probably either scared of hands (if not tame) or he's overly protective of food and the age environment. This is known as cage aggression which can be resolved by long term training and taming.
Do the birds come out everyday for plenty of exercise?- this is another factor is cage aggression, if the bird doesn't spend enough time outside the cage they can become aggressive in this environment. This is known as cage bound.
Also, are the birds clipped?- this can also be linked to aggression.
The diet- seed diets are incredibly bad for your bird and can cause hormonal and behavioural difficulties. Larger birds should have predominantly fresh diets, with small amount of seeds and if easier for you pellets (these aren't everyone's choice but they help you along and I've seen great results with TOPS pellets.)
Are your birds a breeding pair?- this can cause protective aggression.
If this is an issue I would certainly get them checked out by an AVIAN VET for any hormonal or abnormalities
