I NEED HELP WITH THIS PLOT

I have this idea for a book. I've been editing and tweaking the idea but it still has so many flaws. I'm gonna try to fit as much info as I can in this one post so you can help me with plot holes. HERE WE GO!
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A 12-year-old girl named Kayla Minor has suffered from being the middle of 10 children all her life. Often teased or ignored because of her status and misunderstood because of her fascination with tools and engineering, she's been waiting for her chance to prove herself. It comes in a way she couldn't have expected. Her parents suddenly go missing. She and her best friend, Mabel Sweet, go out into the world in a desperate search to find out what happened to Kayla's parents but ultimately to prove themselves to the world.
During the search, Kayla and Mabel find a junkyard. Fascinated by the curiosity of what could lay inside, Kayla says she'll "be right back" and goes into the junkyard. It turns out to be much larger than expected and soon Kayla finds herself lost within its treasures. One good thing comes out of this dangerous escapade, a dirty clunk of metal. Kayla takes it upon herself to fix this ugly, dead robot up and carries it with her throughout her endless search for Mabel. At night she fixes it little by little. By the time she reaches Mabel, she has a new friend. Roam-io is a fairly old model of a robot but being in a more poor, rural area Kayla is very satisfied with it. The 3 of them, 2 girls and a robot head out to discover shocking facts behind what happened to Kayla's parents and the truth behind it all.

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Some problems I have:

1. I have no idea who the antagonist is or what the "truth behind it all" actually is. Sarcastically. Ya know, that would probably be helpful.
2. I actually have names and ages for all her siblings but that is completely unnecessary.
3. When I came up with the characters I tried to create diversity, so… Kayla's dad is African and her mom is Cuban they met when they came to America and shortly had her. Making her a beautiful Afro-Cuban American. I HAVE NO IDEA WHAT TO DO WITH THIS INFORMATION!

and actually, at the moment I think that's it. Please help me fill any plot holes you find and PLEASE give me some more ideas to make this more interesting. OH ALSO! They live in rural America.

Thank you in advance. Y'all are fantastic writers.

Hihihi I'm here to help.

Why would her parents go missing? Do they have some sort of dark past? Is there something special about one of them, or is there something special about their daughter? Maybe they knew something they shouldn't have, saw something they should have ignored. Maybe there's something special about their bloodline or maybe they have some secret duty to the world. Maybe they got sucked into a cult or a time warp or a wormhole. There are so many possibilities!

YAY THANK GOODNESS! Oh also how could I forget, the book is titled Heart of Steel both in the symbolism of the girls' strength and of Roam-io's heart.

Why would her parents go missing? Do they have some sort of dark past? Is there something special about one of them, or is there something special about their daughter? Maybe they knew something they shouldn't have, saw something they should have ignored. Maybe there's something special about their bloodline or maybe they have some secret duty to the world. Maybe they got sucked into a cult or a time warp or a wormhole. There are so many possibilities!

You're right! And as plots go, the reason must also blend well with whoever the antagonist is and what their intentions are. This is my problem. I have neither of those things. Deep sigh.

I can start by helping with the names and ages for the siblings. Is there anything specific you have in mind?

@Natasha I have their names and stuff set but I'm just unsure of what to do with the names. Especially considering the fact that they will only be at the beginning of the book.

Ah yes. Gotcha.

one more thing that idk if it will be helpful or not. This book alternate pov between Mabel and Kayla each chapter.

What kind of story do you want it to be? What laws apply to the world that Mabel and Kayla live in? Is it more science fiction, with time travel or is it more fantasy, with hidden magic? Or does it just stick to the conines of reality? It would be helpful to know

It fits mostly in the real world but just the teensiest bit in the future. Robots exist more than they do today and since now have been easier to get a hold of for yourself. Supply and Demand ya know? In terms of magic, none. Time travel, exists but not for your average person and is still extremely experimental and dangerous.

Oldest to youngest:

Isaac-19 (Rose's twin)
Rose-19
Meara- 17
Michael- 16
Roux- 15
Kayla- 12 (main)
Charlie- 8
Gabe- 7
Mina- 5
Ezekiel- 3

GUYS GUYS I THOUGHT OF SOMETHING FOR THE ANTAGONIST AND STUFF!

Kayla's parents got into financial trouble when her mom was pregnant with her. They needed a house and some money desperately to maintain the 5 children they already had and to prepare for the birth of another one. Her mom and dad make a risky deal with a strange (and smart) woman who has wanted children all her life. They promised that once the girl was born they would give it to her. After Kayla is born however they have more children to kind of hide her from the woman. They avoid her for 12 years and the woman gets so mad that she comes for them. She kidnaps them in hopes that she can lure at least one of them to her and this one she will keep as her fair payment.

(What do you think?)

Ok, so think about this: a relative of Kayla's, maybe the parents or an aunt or uncle or grandparent (or maybe the twins, since the whole twin-bond thing is interesting to explore) is a brilliant inventor and scientist. They were working for a company that is attempting to develop a safer method of time travel so that they can offer it to the public and profit from it, however, they've discovered something unethical about the companies practices, or maybe they're just tired of being bossed around. They escaped the laboratory and are on the run, but the company is determined to get them back. Kayla's parents have either 1. been kidnapped by the company to use as hostages, 2. been forced into hiding by their association to the inventors or 3. are the inventors and are being pursued by the evil corporation. Try that on for size.

That does sound interesting… hmmm…

Alright so during the night and this morning I tweaked and fiddled with your idea @Ellen and here's what I settled on:

Kayla's parents are secretly a part of an organization called the AETT or the Anti Experimental Timetravel Tests. (the name is a work in progress.) The people in this group are constantly protesting and fighting against the harmful tests that scientists and inventors use to try out their time-travel machines. Kayla knows of the AETT (almost everybody does) but sides with George Bennen, her favorite inventor and one of the most famous of all time. He is constantly trying to improve his time machines to make them safer and truly is a genius. One week prior to the test of his newest model, Kayla's parents disappear. The next day so does Dr. Bennen. Kayla knows some of the police are part of the AETT and knows they won't help Dr. Bennen so she sets out on her own, starting by going to his lab in California. After tracing the steps and following the clues, she discovers the secret hideout of the AETT and not only finds Dr. Bennen but also her parents and many many many secrets.

P.S. Isaac and Rose both know about Mr. and Mrs. Minor's position in the AETT and know that Kayla is against it. This is why Isaac is a little harsh on Kayla and Rose ignores her.

I think I'll be alright now! Thank you for all your help!