from his home in the state of Maryland是reporters的后置定语。
his 指代单数名词所有格uncle’s,即 reporters from uncle’s (his) home in the state of Maryland,意思是“来自他在马里兰州家的记者们”。
如果指代复数名词所有格 reporters’,应该用 their,即 from their own (reporters’) home in the state of Maryland,意思变成了“来自马里兰州他们自己家的记者们”,也就是记者们本人的家就在马里兰州。