Books that heavily explores the concept of empire expansion through colonization, political marriages and migration

Whether it be diplomacy/trade or warfare. It has to be about expanding/conquering empire.

Yes. I already read Wheel of Time and Malazan. I am also not interested in ASOIAF (i read upto some of book 3) cause i know it does have what i was looking for. Now that is out of the way.

I mostly prefer to see the political marriages especially between the conquering empire and the about to be conquered land/faction. That sounds like fun concept. Or i mostly enjoy cross-culture marriages

Any recommendation that explores these the most? Thanks