Hi Emma! Sonny is a cutie
Yes, he's a boy
The patchy appearance of his cere is due to his pied genes--he is a combination pied budgie, which means he is has both recessive pied and dominant pied genes. This is why part of his cere is the usual "recessive pied" colour (pink) and his chest doesn't have any green on it, but also accounts for the "dominant pied" irises in his eyes (I believe I do see his iris rings in that first picture you just posted).
He is a dark green combination pied budgie