I went fishing with both of my fathers-in-law.

fathers-in-law 是复合名词 father-in-law 的复数形式。father-in-law 由 father（父亲）和 in-law（法律上的）组成，指"配偶的父亲"，即"岳父"或"公公"。 复合名词的复数形式通常在主体名词后加复数词尾，所以 father-in-law 的复数形式是 fathers-in-law，而不是 father-in-laws。