Brakes

You're going to have to do some troubleshooting to determine why. Get the front wheels off the ground when they are frozen. The crack the lines at the master and see if that releases them. If not, try the same at the front bleeders. Make sure you didn't contaminate the brake fluid with even just a drop of any oil product. What are the symptoms? It's summer, so I doubt anything is frozen. What have you tried so far? Do the front wheels turn at all or do they skid? What does the rubber bladder seal under the master cylinder cap look like?

You have to see if the calipers have frozen pistons. You may need calipers, pads and rotors

Black and dirty is not desirable, but it's not the "kiss of death" either. What we don't want to see is the rubber seal blown up and mushy, and you can't stuff it back into place. That's a sign the brake fluid is contaminated with petroleum product such as engine oil, transmission fluid, or power steering fluid. That gets to be a REAL expensive repair.

The reason I went there first is GM doesn't have a lot of caliper trouble and to have two stick at the same time is really rare. Contaminated fluid will lead to both calipers sticking, but if that doesn't appear to be the case, consider the brake light switch is misadjusted and is holding the brake pedal down a little, or something else is preventing the pedal from returning fully. That will trap brake fluid which will keep the brakes applied, cause them to heat up, the fluid will expand, and apply the brakes even harder. The place to start is by crawling underneath to open the bleeder screws on the calipers. If that causes them to release, you have to look for where the brake fluid is being trapped. If they do not release, the pistons are sticking in the calipers or something else has the wheels locked up.

If you have a 4wd model, they use a solid transfer case, not a viscous coupling like Chrysler and Ford so if one wheel is locked up, the other one won't turn either. You listed a 2wd model so that shouldn't be a concern.