I would start to look for possible causes and keep a close eye on him
Are there any scents that could be irritating him (scented litter, air fresheners, oils, perfume etc), is the bedding dusty?
How does his breathing look - is it laboured or requiring more effort then normal?
When you hold him up to your ear and listen to both sides of his chest what do you hear?
Hes fine other than that. He does still do it and his brother does not. We've had them over a month now. No labored breathing. No dusty bedding. He's very active and happy. It doesn't seem to be getting better or worse.