Okay, so if Matt and Shiro graduated together, then imagine the age difference between Matt and Pidge. That is 10 years. This is giving me an intense need for half-sibling Holts.
Hear me out. What if Mrs. Holt is Matt’s step-mom? Mr. Holt may have had Matt with another woman, who then left him or died (idk which is better). He would have then been too busy having a job as a scientist and a single father to start dating again.
Cue (soon to be) Mrs. Holt. Maybe she went to a conference he was presenting at. Maybe they were lab partners. Maybe she was Matt’s teacher. Who knows? But they met, and even though they obviously liked each other Mr. Holt couldn’t make the time to date… until Matt made it known that he adored Mrs. Holt. Who could say no to that little dork that gets excited over Space Ice?
So they start dating an all is good. They get married and later Katie Holt enters the world.
Now comes to the point where Matt becomes a big brother.