<p><my neighbor,=“” and=“” his=“” son,=“” [is=“” are]=“” nice.=“”> Which should it be? “and his son” is sort of parenthetical, so I’m not sure if it should be included as the subject of the sentence.</my></p>
<p>is, but why would you say something like that? Just say my neighbor and his son are nice…problem averted.</p>
<p>As gerturde mentions you would say “My neighbor and his son are nice”.
You cannot say “My neighbor, and his son, are/is nice”.</p>