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? YeRMSSu+b74Dd9t+ZMxoFWaIGAGQ5wrlypiaLvvu4za44qgJslLwS+xFBlso5XRU