问:我姑妈是个孤寡老人,为了安排自己的养老,她与我的堂哥约定,由堂哥为她养老,她将来把房屋留给堂哥,两人还立下了字据。这两年来,堂哥对姑妈的态度逐渐恶劣,于是,姑妈想让我来赡养她。但堂哥却以立了字据为由,不同意再改。请问,立了字据的协议能改吗? Q: My aunt is a lonely old man. In order to arrange her own pension, she has agreed with my cousin that her cousin will provide her for her old age. She will leave her house to her cousin in the future. In the past two years, cousin's attitude toward aunt is getting worse, so my aunt wants me to support her. However, cousin has set a word on the grounds, do not agree to change. Excuse me, the agreement that established a letter can change?