Do u think mario and Luigi act like each other as a response to trauma?
I don't think so, but i do think that they...
Pick up on a lot of each other's habits by virtue of being brothers who lived their entire lives together
Find each other to be inspiring in their own special way
Luigi has a strong desire to be brave like his brother. He pushes his own boundaries while following after him, and exhibits shame in his inability to defend himself.
Meanwhile, we can see that Mario makes a conscious effort to play it safe and keep his mouth shut much the way Luigi does... even though Mario often ends up caving to his own bullheaded determination in the end.
I think instances where they act like each other are less a trauma response and more an effort to self-comfort and find balance.
Based on leaked concept art for the movie that showed Peach, Daisy and Bowser in a 80s highschool setting. Although I don't think it would've fit the movie, I still wish we'd have had some form of Bowser backstory. Maybe in the next one!