Help me out please? what can i with this life?

am 15 now.. my parents buy me anything which i want but they dont really spend time with me. my mother goes in her way and my dad is in abroad and comes sometimes.. i live in india.. am not allowed to make a b.f am not allowed to get attached with friends.. my cousins are like my body guards they just know every secrets of mine and pass to my parents.. i get everything i need,,,, but my dad loves his uncle's son he is married... the couple often comes to our house i mean everytime you know they are just 20 and 23 that girl and boy... my mom makes her food i have to share my clothes with her now they come to our house and stays for 3 days sometimes..and my dad just take good care of them..they all have dinner together and am not allowed ... i should talk to her and obey that married couples they just come to my room and mess my room...my dad and mom insults me infront of them..that girl is given food first before me..i dont understand why?? even my dad is behind them and acts like he is the father of dat couples you know it hurts really a lot..he tells me am not worth it.. and my mom is jelous of me.. really i swear,... she is not my step mom...she loves my younger brother she hates me coz amm a girl...