Doors and Windows - wood used to build the door frame jamb

I'm expaning a single interior door to install french doors and was wondering what kind of lumber should I use for door jamb. I've used pine boards to build the frame but not sure if I can use the same to build the jamb. This is a 2X4 wall. thanks

Jamb stock (with applied stop or rabbeted) is readily available.

If you have something "special" in mind for the jamb: a guide is match the species of the doors. (Doors & jamb will have the same machining characteristics, finish [paint/stain] qualities, and screw holding ability).

Softwood picks: birch [machine ++ finish ++ screw ++]
Poplar [machine -+, finish -+ screw ++]
Southern yellow pine (not all pines are equal) [machine ++, finish ++ screw
-+]

Not sure what you are asking, but you will likely need to change the header over the door. Even if it is not a load bearing wall, some sort of header is needed to prevent sag. The is usually done with 2x4 or 2x6(or larger if a supporting wall) lumber. As suggested above, premade jambs are easily available at home stores, lumberyards.

Thanks a bunch. I will look for the kit. I'm assuming they have it for french doors as well...
PS: I put in a strong header (2X10). I'm sure much stronger than I needed given this is not a load bearing wall but I thought, now that I had things gutted out I might as well do it. thanks again.

2x10 sounds good, even for a load bearing wall. Look for jamb kits in the size you need, probably 5' or 6', for 4 9/16"(standard) jamb widths.