A few people actually wanted to know more about Finn's past (my headcannon) so here goes
"Wake up little brother!" a black Aston Martin Zagato said, shaking awake Finn McMissile, a blue metallic DB5 from his sleep. "You're friends will be here soon!"
"Rhiannon, stop.." Finn groaned. "Wait, my friends?" He was fully awake now.
"Come on. Mum's got breakfast going." Rhiannon smiled as Finn jumped down from his bed. He followed his big sister down the hallway of the big house. He saw a green Aston in another room.
"Morning, Ben!" Finn greeted as he passed.
"Morning, Finn." Ben answered back.
Finn followed Rhiannon down to the kitchen where his mother was over by an older style stove.
"Morning, my little Finny boy!" She smiled, hugging him.
"Mum.. stop." He groaned, squirming from her grasp.
"Oh, alright." She laughed and went back to the stove.
A dark blue older Aston Martin came in through the back door.
"Morning, my dear boy!" He said, seeing Finn and giving him a small bump on the side with his tire.
"Morning, dad." Finn smiled.
"He likes you more than me." Finn's mother, Tracy joked, turning away from the stove.
"Because I don't call him 'Finny boy'." His dad laughed.
"Oh, James." Tracy rolled her eyes and gave him a small peck on the cheek. "Is everything ready?"
"Sure is." James said. "They should be here soon."
"Good, because breakfast is ready." She helped Rhiannon set the table.
Soon after breakfast, Finn left to prepare himself for his friends. He cleaned up his room a bit and made it presentable.
"Finn!" They're here!" Tracy called and Finn raced downstairs. Leland Turbo, a red Jaguar, and Siddeley, a private jet, were there waiting for him along with Siddeley's parents.
"Hey Finn!" Sid greeted.
"Why don't you three go play in the backyard?" Tracy suggested. "We'll call you when lunch is ready."
"Alright!" Finn led the two in the backyard to a large field they always played in. Finn drove up on a large rock in the middle on the field over the tall grass. "We're all secret spy agents." He declared. "We must go on a mission to find the bad guy, Professor Z!"
"Where is he located?" Leland asked, playing along.
"He, is in the woods." Finn replied, pointing his tire to the wooded area surrounding the property.
"D-do we have to go in there?" Siddeley asked timidly.
"If we want to get him and protect the hostage, yes!" Finn said. "Come on!" He jumped off the rock and led them towards the trees. Halfway through, they stopped.
"He should be around somewhere. Keep close." Finn said, sneaking along the dirt floor. Leland nodded eagerly as Siddeley gulped, not liking the idea.
Suddenly, a small tree snapped and began to fall, aiming for Sid. He shrieked and reversed before it could hit him.
"He's attacking!" Finn yelled and he and Leland pretended to shoot at the empty space by the fallen tree. Sid raced out of there quickly and soon Finn and Leland did too.
"We need to find another way in." Finn said, thinking to himself as Sid tried to catch his breath.
"Maybe try to sneak behind their hideout and catch them off guard?" Leland suggested.
"No, they already know we're here. They'll have guards everywhere." Finn said.
"Can we go back?" Sid asked after finally calming down. "I'm getting kinda-" He got cut off by an explosion off in the distance. The three looked to where they saw a large cloud of smoke with fire erupt in the distance. Finn quickly drove up on the rock he was on before and tried to look over the tall grass of the field to see what happened.
"Mom.. dad..." Siddeley said quietly. Almost in an instant of the cloud of smoke disappearing in the sky, they heard a group of gunshots echo through the air. The three friends looked horrified.
"No!" Sid screamed and tried to race back to Finn's house but Finn grabbed him and stopped him.
"No, Sid. Don't!" He said, holding him back.
"L-let me go! M-my.." He didn't quite finish his sentence as he burst to teas, the gunshots continuing. Still holding Sid back, Finn shut his eyes and hugged him the best he could. Leland joined in for a group hug.
After a short while the shots quit and all was quiet. Sid wanted to go but Finn refused.
"Wait just a second." He whispered. He had a bad feeling in his tank the same as Sid, but they all waited a while longer. Sid couldn't handle it anymore. He squirmed from their grasps and raced off back to Finn's house.
"No, Sid!" Finn yelled and raced after him, Leland following closely behind.
Sid stopped at the back of the house and froze. Finn and Leland came to a stop behind him.
The front of the house was on fire, and it had a huge gaping hole. Dead corpses lay on the ground, of both Finn's and Sid's family. Each one shot multiple times. The three could only stare. Finn slowly edged up to his mother and nudged the body gently. Getting no response, tears began to escape his eyes. Sid's too. Leland came up to them both and hugged them tightly.
After almost pulling themselves together, Leland managed to phone his parents who couldn't make it to come and get him and explain what happened. Finn nor Sid could speak a word about it, so Leland told the police everything that happened, from the point he came to his house to the point where he stood in front of the cop. After all the tiring business was over and the bodies taken to be fixed up and buried, a very tired and emotional Finn and Siddeley went along with Leland's parents, who agreed to be their new guardians, though they still kept both their last names.
Okay so I know that was a very terrible way to end it but the lasttwo paragraphs were legit straight from my head since I had no more room in my notebook.