Am I wrong for not going out of my way to help?

So basically my husband has 3 brothers. My husband and I have been together for 10 years and married for 5. We have two kids and one on the way. Our oldest has autism and so my days are spent doing therapy and schooling with him and taking care of my two year old daughter. I'm a SAHM but my husband makes more than enough money to support us so we live very comfortably. This pregnancy is high risk due to 3 previous consecutive miscarriages. So I have a lot going on in my life at this moment. My husband and I get along really well with one of his brothers and his wife. They have a young daughter and she is pregnant again with their second. His other two brothers however have never really liked me. They dont say why but I know it's because I'm a SAHM mom and I should be working. They also look down on our autistic son. One of the brothers birthdays is next month so the oldest brother is throwing a surprise party for him. He sent out fb invites and invited everyone else in the family (spouses too!) except me. Just my husband. I have no idea what I could have done to make them hate me so much but it upset me. A week after this the oldest brother (who is planning the party) texts me! He tries to make small talk but eventually gets to what he wants. He wants to take his wife to Brazil and surprise her by renewing their vows there. Because both my parents are Brazilian and I speak fluent Portuguese he wanted ME to call and book him hotels and a photographer. I texted back that I would try but I'm very busy and I can't promise anything. He said ok. Two days later our dog (who we have for 10 years) is diagnosed with an aggressive form of pancreatic cancer. Two days later we had no option but to put him to sleep. I made a Facebook post to let people know and NOT ONE of his family offered any condolence. The oldest brother has now been going around talking more smack on me to everyone in the family because I didn't call the same day he wanted me to even though I was at a hospital appt all day with my son! Am I wrong? Are they right? Why do they hate me so much?!