小明要办个聚会,他邀请了他父亲的姐夫,他姐夫的父亲,他哥哥的岳父,他岳父的哥哥。请问他最少邀请了几个人? 5YjMCSk+XKp3pulX8u2cxi/JO0aErDkWoBwk8pU7h302j7NrTh5WVdgWEDMz82y0