Psychoanalysis headcanon: When Wrench and Hammer were kids their parents would argue loudly. Wrench didn’t know what their parents were saying but he could still tell that they were yelling and it made him feel bad, but Hammer heard almost every word of their fights and it really affected him. Wrench would ask Hammer to tell him what they were fighting about, and Hammer would give him a vague overview but he wouldn’t go into detail because he didn’t want Wrench to hurt the way he did. Hammer didn’t want to burden Wrench with any of his other problems either, so he kept his emotions pretty much to himself, and Wrench, seeing how reluctant Hammer was to talk about sensitive stuff, bottled up his feelings as well. However where Wrench is capable of working through his issues without talking to anyone about them, Hammer would just pretend everything was fine, and his problems never actually went away. This (as well as a lot of other stuff probably) led to Hammer being the more insecure and emotionally stunted twin.