Thanks to other players who have posted on this forum about how dynasties work, I already knew that the offspring of my arranged marriages might ally with their mother's faction.  However, I had two male grandchildren who's grandmother had her life cut rather short and her entire empire was under my control.  (I actually took her best daughter and then declared war and killed the entire kingdom!  lol)  Both of the male grandchildren decided to ally with the long dead faction.

This shouldn't happen--or if it should happen, then the boys ought to get out and run toward the nearest neutral territory to make themselves a new city and restore the fallen kingdom.  That would be pretty cool, actually.  As it was, the boys just grew up in my capital and stood there blocking caravans, but doing nothing else.  I had to come and kill them off because I was unable to negotiate peace with them either.

Plus another faction keeps pestering me to arrange a marriage with his faction, despite the fact we both only have girls to offer.  (I checked, but he didn't like the idea of girls getting married to each other!)  The other factions shouldn't pester you about arranged marriages unless there really is one available.

Last but not least, I'd sure love it if our children or grandchildren could marry other random heroes that I find, because I can no longer marry off any of my grandkids, due to all the boys needing to be exterminated so uncerimoniously