I'm 25 years old I love some one but his parents are not willing on our marriage they want him to marry his cousin please help me what should I do. Should I leave him or how he could convince his parents

How does he feel about defying his parents?

It's obvious that your culture is different that normal, where the parents decide who their children will marry. Unless he's willing to go against his parents wishes, and end up alienating himself from them, I don't see a resolution.

His parents have made it clear that you are not what they want for their son.

I think the best thing to do is forget about him and move on, or hope that his parents change their minds.

His parents say after two years we will think about this matter and my parents want my marriage this year
I can't forget him its not that simple you said n you did

You didn't say that his parents would think about it in 2 years, you said that they're against your marriage to him, that they want him to marry his cousin.

So which is it? If they're willing to consider it than it's not them that you have to convince. It seems that it's your parents that are the issue.

No my parents are willing his parents said this because they know my parents will not wait for two years and after my marriage they'll say we were willing but her parents did'nt wait

My mother is ill and I'm the only one remain unmarried among my siblings and she want me to get married as soon as possible

Well it seems that you only have to convince your parents to wait an extra year, than you can get married to the man you love.