Edited to reference your brother - sorry!
I can understand where you're coming from, a bit. Let me tell you about my sister and me. I was the first of my siblings to have children and my oldest was 11 when my older sister had her first. She and her husband are both very successful, live a very comfortable life and are able to provide their children with more opportunities than I am able to provide to mine (frequent vacations, private schools, etc.). I'm not jealous of their success because I know it's the result of a lot of hard work, self-discipline and good decision-making. Like with you and your brother, there was a long history of subtle, snarky jabs over the years about how my children behaved, what they ate, whether or not their manners were up to her standards, etc. all delivered with the implication that *she* would do better, and that her children would always have impeccable manners, be gracious guests, would eat anything presented to them, would never need a nap at an inopportune time, wouldn't cry or whine or fuss, etc.
As you can imagine, real life is different and her kids are...normal kids! One has selective hearing and ignores much of what my sister says, the 4 year old has yet to make it through a holiday dinner without needing to leave the table due to getting bored or acting up, they're both picky eaters, one is pouty....I love it! They are normal, adorable, sweet, loving, imperfect kids with quirks and limits like every other kid, mine included. I certainly don't say anything but in my head, I sometimes think "now you know what it's really like" and every now and again, she'll actually come to me for advice or reassurance that something is normal and gets better, or that I saw something similar in one of my kids and thought it worth getting checked out, etc.
I think that you'll find that your brother comes down to earth when dealing with a crying, fussy, poopy baby. What's more humbling than parenthood, right? Even if they can hire an army of help (like my sister did) at the end of the day, they are still parents just like you and has no idea what's coming just like you didn't and will have to figure it out and do their best, just like you. He may not ever acknowledge that he was judging you or apologize for his comments, but my guess is that as he settles into the reality that no child is perfect, he'll treat you with a little more respect and will hold his tongue on the snide comments, which might help you heal your relationship.
Another thing to consider is why their comments bother you. My sister's didn't really bother me because I knew that if she ever had kids, she would realize how unrealistic her expectations were and get off of her high horse. My other siblings and I used to joke about it (and still do). I was confident that I was doing a good job and that while my kids certainly have their challenges, I was confident that I was equipped to help them meet those challenges. Don't let their comments make you feel insecure. If you've been at this for 14 years with no disasters, you're doing more than fine.
My advice to you is to go through the motions of welcoming your niece or nephew - send a gift, visit if they live nearby, and let yourself fall in love with the baby. Be kind to your brother and his wife even if they is still obnoxious and have faith that they'll come around when they realize that parenting is a lot harder than they thought it would be.