They are not allowed to force you. Be kind with them and tell them the results of such a marriage.
The wife will not be happy and neither will you and this would cause problems in the family.

I am a Muslim male. I respect my mother so much but a few days back she told me that she had talked to her brother about getting his daughter married to me. When I said I don’t want to marry her, everyone stopped talking to me and started cursing me, saying that I will never get success. In this situation, what should I do? I really don’t want to marry her. How do I explain this to my mother?