I had an exit row aisle seat in coach picked long in advance, when a lady seated in a middle seat behind me, asked me to switch, so she coluld sit next to her husband in the middle exit row seat next to me. They had gotten on just as the doors closed, so I suspected, that they were standbys!
Of course, I said 'NO'!
The husband had a pushy attitude the whole flight.

On a recent flight, I was in the bulkhead aisle seat in First ( apparently your favorite also), and a women suggested, that I trade for her window seat in the row behind, so she could sit next to her husband, who was next to me.

Of course, I said "NO'! But she was loudly verbal about it in raising a stink to get her way. Eventualy her husband moved back to be next to her, and she talked through most of the transcon. And even had the nerve to remark to me later about the situation. WHat nerve!