Conduit/wires to panel box
The short answer is yes you can run 2 circuits in 1 conduit. There are some limitations depending on the size and type of wire or cable and the conduit size. If you provide the needed ampacity of each circuit and conduit size / current wire type we can provide you with what would be allowed by code in the areas we know (providing your country / state) we may be able to get quite specific.

Added:

See the comment below but you have way more room to add circuits with the wire you mentioned. You should be using wire listed as THWN most of the wire I purchase today is listed as THHN /THWN.  THWN or wire listed for a wet location  is required when the conduit is outside or a wet location. Illinois is on the 2008 NEC. The wire size, fill and type have not changed for years. Note source for NEC In ILLINOIS is the NEC In effect 1-1-2017.
Good luck and be safe.
2nd note I was lazy and used table values for #12 since there were 2 sizes. 1/2" THHN / THWN the max conductors for #12 is 9. The max fill if they were all #14 is 12 , with 12 conductors the derate would be 50% so as long as you stay below 9 conductors your wire size and ampacity is not affected.