ChargedInfluence, please get all the help you can.

Although not suffering from any mental illness, I've had these feelings too. Mother who thinks it's fine to belittle me although I've taken her to medical appointments, shopping, sorted out benefits, etc. Aunt (her sister) gets involved in things that don't concern her yet but hasn't got time to listen to me. Brother who is mother's favourite, despite lack of interest in her welfare. My mother blames her attitude of her mother's inability to parent, having favourites. Only person I've any time for in my family is 14 year old niece. Sadly too young at moment to make her own way in life!

Your situation is not your fault. Often other relatives don't want to help for fear of taking sides. We're all entitled to have some dark thoughts, how we deal with them is an indication of our character. Hope this makes sense.