I am wondering if anyone can give me some advice or just to talk to about this issue I have. I have one sister who I have not spoken to in 4-5 years, we live in the same city but from a long series of issues I have chosen to not associate with her or her husband or any of her family.

I will start off saying, so that I do not seem to be misleading or anything. my husband our toddler and I currently live with my parents. We purchase the groceries and pay for the internet, cable and phone and do all cooking and cleaning, automotive work and anything else that needs to be done. My father refuses to accept money from me, so we 'give' it to him in other ways. My husband had a custody issue that was very financially difficult for us in 2005 when our daughter was born. Therefore to help both my parents and ourselves we have moved in with them. As a mutual agreement we are staying until we can afford to buy a house of our own. Meaning no co-signor all our own money etc.

Some basic info i am 29 went to college, worked full time for last 8 yrs work at home part time for last 2 yrs, married with 1 toddler and 1 step tween.
My sister is 34 never finished grade 9, married but separated but still living with her husband for welfare fraud reasons, has 3 boys 17,14,9 and has only worked for the last 3 yearsat may different jobs, her husband has had so many jobs i can't count them nothing stable.

My issue is my Mother coddles my 34 yr old sister constantly. My sister is not allowed in my parents house anymore from previous issues.
A short form of the main problem is from 1990 when my first nephew was born my mother has paid for everything for my sister. She has 3 boys who are now 17, 14, and 9. She lived with her in laws for 10 years and my mother bought her groceries, paid for all car repairs, bought 'new' used vehicles for them, bought all clothing and gave her money when ever she needed it. In 2002 my sister was evicted from her in-laws house (her in-laws had left the house 6 months previous as they could not afford the mortgage and signed it to the bank) My sister lived in the house for 5 months with no heat or electricity other then power cords from the neighbours which they knew nothing about. They had a hole in the bathrom that went directly to the sump pump area and the house was covered in mouse feces and fleas. I had the pleasure of seeing this house as my parents were given custody of my nephews and we need things for them. My parents then had to purchased brand new everything for 3 boys as all of their things were destroyed. My father had just been layed off a job he had for 32 years so money was not the same as before. My mother failed to see this though.
In 2003 my sister went to CAS and got her boys back when she was living in a 1 room motel room!! My mother then helped her get all new things and paid for a place for them to stay. In 2006 my eldest nephew moved in with my parents as he was in trouble with the police. My parents then had to purchase everything brand new again for him. My mother spoiled him rotten, he never went to school or lifted a finger around the house. My father kicked him out this past July for coming home drunk at 16. There were many issues leading up to this but that was the last straw. My eldest nephew would visit his parents on the weekends who live in more of a country area and they would supply him with dope that he would bring home and sell to the kids in our more 'town setting' area.
My mother is always secretly talking to my sister, either at work or goes and calls her from another room. My father checks the bank account and sees amounts being taken out but does not know what it is for.
I overheard a conversation this evening of my mother helping my sister for christmas this year (again)
I do not understand why my mother keeps doing this. I have never asked for any money from my parents. my husband and I supported ourselves for 10 years while paying a large child support payment, we bought our own cars and paid our own rent, We were adult doing what adults do. Being responsible for ourselves. I do hate having to rely on my parents this way, but i will not ask for any money. My sister has no problem with it at all.
The one time that I had brought a money issue to my parents was during our court issue. I was stressed and needed some advice. My mother flat out said we can't help you financially, we have no money. I wasn't asking for money, we were thinking possibly increasing our existing loan, we were checking that if we needed a co-signor to increase it would they be able to do it. We ended up having to cash in our RRSP's. That made me so mad, we never had them as a co-signor for anything and my sister took them to the cleaners on 6 different loans!!!

Am i not seeing something that is right in front of me, Why does my mother help my sister so much and has always flatly refused me, even when it is a situation that i did not do myself. My father does not approve of giving my sister anything but he can't prove it and gets sick of fighting about it when he can.

I feel and wonder what did i do wrong, is it because i am the youngest? I am second? Did she screw up with my sister?

Sorry this was so long this has been years stored up in me. And there's still lots more but this is the jist of it.
Can anyone shed some light and help me understand what i have done wrong or different.