As title says, could it happen and how do you think it would work? I guess it would be possible if Alexander I have two legitimate surviving sons (say Alexander jr. and Paul), and wants both of them to be monarchs. Alexander, unlike his brother Nicholas, never bothered to crown himself as King of Poland (Nicholas I was crowned in Warsaw in 1829), so he could decide late in his reign to let his younger son to be crowned instead. Such Romanov king, who is not Russian Tsar at the same time may change few things-he would reside in Warsaw, would remain Orthodox, but could marry Catholic princess and have Catholic offspring. Most important change is Nicholas I butterflied away as tsar, (perhaps his alternate nephews would happen to be more liberal), so more chances to avoid November Uprising (although it still could happen, Wysocki and his frustrated buddies would not disappear, but may not gather enough support ITTL). Nicholas I was old school monarch, who treated his job seriously, so if he tought, that welfare of his subjects require breaking Constitution, he didn't hestitated to break it, in absolutely good will. That view was not very popular among Poles, rumours, that he wanted to send Polish Army to Belgium to use opportunity of absence of Polish troops to abolish autonomy of Congress Kingdom also were not helpful.