Jealousy..?

Morgan
Ok, before I begin, let me give a little back story..
My brother and his wife have been together for nearly 2 years, and 1 of those years is marriage. They met and started dating Dec. 1st of 2013 and decided to get married the same day of 2014. (My husband and I have been together over 3 years and will have been married for one year on Dev. 6th of this year.) So my brother and his wife got married secretly 6 days before us so they "wouldn't take our day" and then never told us about it. (I actually found out about it through the person that does the marriage licenses in our town, because I used to work with her) My sister-in-law was also 8 months pregnant with their child when they got married, and had the baby December 28th. (She had 2 from a previous relationship, and this was their first child together.) 
Even though what they did upset me, we've always been able to get along and hang out a lot, and talk a lot. She even joked about my husband and I needing a baby by the time our nephew turns 1. (That hasn't happened, and won't, we are waiting for a few years) But the twist is, she is now pregnant again..and they didn't want to be.. They just obviously did nothing to stop it, but they didn't want another child, they only wanted 3! And I think I'm slightly jealous. I have crazy baby fever and it's dumb, because my husband and I have clearly talked about waiting until we are settled in our new house for a few years before kids. But my brother and SIL won't even talk to me right now. I have no clue what I did, but they keep rejecting my offers to come over to the new house, and they didn't even invite me to my brothers own birthday dinner yesterday. I'm slightly jealous of their baby, but I'm also very hurt that they don't even want anything to do with me, when all I've done is help them anyway I can..
I kinda just needed to vent, but if anyone has some advice I'd really appreciate it. All of this is starting to depress me, and I'm not sure how to handle any of it..