I would be interested to know where you researched in order to come to the conclusion that the “Church” is called a brother. What do they mean by "Church"? The prodigal son does has an enormous dispensational message for those with eyes to see & ears to hear.
The prodigal son is about Jeremiah 31:31 - (the house of Isra’el & the house of Judah)
Jeremiah 31:31 [ A New Covenant ] “Behold, the days are coming, says the LORD, when I will make a new covenant with the house of Israel and with the house of Judah—[NKJV]
You might want to read & research the post I just left on a couple of other threads that are bashing Mormons.
http://www.freerepublic.com/focus/f-religion/2793224/posts?page=16#16