the broilers and cornish X (cornish X being a type of broiler, broiler being a generic term nowadays for fast-growing meat birds) are not bred to live long, healthy lives, or produce lots of eggs. with extremely careful management and feed restrictions, they can reach maturity, but they're not "supposed" to, and yours probably won't. their muscles literally outgrow their bones. at 4 months, your bird has already lived longer than most broilers do. i agree 100% with what itsy said... it is what it is.
this is a conversation you are going to need to have with your grandchild (or grandparent? sorry, not sure). given that your bird is already displaying health issues, your choice is to end its suffering now, kindly, and perhaps get a meal and a respectable lesson out of it; or let it suffer. =/
edit to add: if you look at the stickies at the top of this forum, there's some great threads about butchering your own birds and how-to guides. if you can't do it, sometimes you can find places that will butcher and process your birds for you (for a fee). you'd have to do some research in your local area. or you might try putting up a craigslist ad or something, tell your story and ask if anyone with experience might be willing to help you out. or you could give it away to someone who would butcher it for their own table. or if you can't find anyone to help process it, you could just put it down and safely dispose of the meat.
