Your cousin-in-law is an A........I guess I'm not supposed to use that word on TFL. Thank you for refusing to hunt with him. When he gets tired of finding new hunting partners, he'll hopefully quit hunting.
Would I hunt whitetails with a 9mm? Well....no. I was guiding a friend who shot a small buck with an '06. I brought my Browning HP to dispatch any wounded critters. I wanted to concentrate on helping him, not filling my own tag. As we approached his dead buck, a doe and fawn got up in front of him, and ran crossways in front of me at about 25 FEET, I put a 124gr hollowpoint into her front shoulder and lungs. She went down, and had we been at rifle distances I have no doubt we'd have found her dead. As she was so close, I walked over and shot her again in the head.
I have also used the .44spl/200gr Gold Dot @ 800fps from my Super Blackhawk to take both whitetails and mulies. They died. Fast.
You'll probably never NEED a gun. I hope you never do. But IF you do, you will need it worse than anything you've ever needed in your life.
IF we're not supposed to eat animals,
howcome God made 'em outta meat?