When this woman is concerned for her "crazy single sister" she asks Reddit:
My (34F) sister (31F) has always been jealous of me. It's put a lot of strain on our family over the years, especially because she tries to displace her feelings elsewhere.
For context, I met my husband in college and we were married 9 years ago. He's always been able to support our family of 6 - 4 kids between 7y-18mo - and I've been able to devote myself to my family entirely as a SAHM.
I not only take care of the family, but also go to PTA meetings and am involved in the school community as well.
My sister, meanwhile, has none of this. She claims she doesn't want kids, and has never been able to make a relationship work. She was in graduate school for a while, but claimed that it made her miserable, so she dropped out without even finishing a degree.