I have found many odd coincidences between the two's storylines/other stuff.
First:
The city is being monitored, many changes, people being jailed for rioting and all, then some rebels working to get it better.
Second:
Endings
Games end on a huge tower, after climbing up the whole thing, then you meet the guy behind it (Breen/Jackknife) and you kill them, then there is something that almost kills you and whoever you're with (Generator exploding, GMan saves you, along with Alyx/Helicopter out of control, Kate flys out, you jump out, save her, then the helicopter explodes.)
Third:
People captured to lure you to the big tower.
Forth:
Organization sending out troops to kill you. (Combine/Security place)
Odd, right?