I've seen alot of problems with multiple aliases in that a player will make 2 or more aliases, practice on one, then go to the other "clean" one to bolster their stats against noobs. Especially in the games where rank matching occurs, so your alias looks noobesque, but in reality your skill level is master of all things <said game>. So, the rank increases artifically because the noobs are being dominated at an extreme rate. Now, perhaps, if all of the aliases on the account are "averaged" together based on how well you are playing at the time, it will know that you are player X and not player Y for the time being. It would probably take a game or two for it to catch on.
What might work is if the game "stores" the results of the past few games and uses those values to "place" the stats into the appropriate alias. There would have to be a fairly large gap between skill levels mind you, but typically players have their own ways of doing things and that could be a way to separate the "fame farmers" from the individuals in the household.
This all sounds like a lot of extra work for a very small minority of players. If it were me and my spouse, I'd just let her use my account and screw the stats. It's easy enough to keep track of whose stats are whose because it tracks every game, who was played against, and other details like that.
Easiest solution, spend the extra $$, support the company that made the awesome game you're wanting to play and be done with it