LOL zero of this stuff affects you personally and you sound utterly self-absorbed to think it does. Have you ever stopped to think that perhaps Natalie doesn't like you? It sounds like she puts on a polite face when dealing with her difficult in-laws, but your disdain for her is so strong that I'm sure she's noticed.

For whooping cough and something else. I've never had to get shots before seeing a baby, and I have no idea why I need to now to see my own nephew.

You seriously can't fathom why your Brother & SIL don't want their newborn baby exposed to life-threatening, preventable diseases? Were you raised in a barn?

Not to mention, she is going to be a stay at home mom now, so Kevin will be their only source of income, which I think will put way too much stress on him.

Guess what? No one cares about your opinion. Their family planning is none of your business and you are going to permanently damage your relationship with your brother's family if you continue this thinking.

My recommendation to you OP is to visit a therapist to work out why these things bother you so much. Are you jealous of your brother's life? Do you feel the need to be the "matriarch" now that your mother is gone? You've got to figure it out, because the petty anger and resentment you're harboring is quite troubling for a 38 year old woman. It will tear you to the ground if you don't face it head-on.