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? IlAWa1lUlyo7wOjZxMNLK3Yi//QeBO1kwYSk6/8T2azBul2JJADrlQJX5V1ib8a+