Yes and No. You can if you work at it use both connection. You have to in effect tell the computer which sites you want to access with which connection. So you could run youtube on one and your game on another. You can't really combine them because they have different IP addresses and even if you get past that they have different latency.
Look at the ROUTE command if you want to attempt this but be aware you can only have 1 default route in your machine and must remove the other.