You can use their widths if they are divs.

1. First find the width of the parent element:

document.getElementById("parentElement").offsetWidth

Note: This is just an example because you haven't provided the code of these divs so you may have to change this a little accordingly.

Here, we are finding the width of the parent element.

2. Find the width of child element:

document.getElementById("childElement").offsetWidth

Here, we are finding the width of the child element.

3. Find the proportion:

let parentWidth = document.getElementById("parentElement").offsetWidth;
let childWidth = document.getElementById("childElement").offsetWidth;
let proportion = childWidth / parentWidth;

Here, we are dividing the child elements width by the parent elements width so that we can get the proportion by which we have to size the element.

4. Use the scale() property:

let parentWidth = document.getElementById("parentElement").offsetWidth;
let childWidth = document.getElementById("childElement").offsetWidth;
let proportion = childWidth / parentWidth;
<Parent style={{transform: "scale(2)"}}>
  <Child_1 style={{transform: {`scale(${2 * proportion})`}}}/>
  <Child_2 style={{transform: {`scale(${2 * proportion})`}}}/>
  <Child_3 style={{transform: {`scale(${2 * proportion})`}}}/>
  <Child_4 style={{transform: {`scale(${2 * proportion})`}}}/>
<Parent />

And there you go, by using the proportion variable to dynamically change the value of the scale, you can easily achieve what you want!

Now, a few concerns:

Given, that this code works in theory I can't say that it will work for you since you haven't provided any code in your question. This is bad, and make sure you provide the code from now on. This is only for your own good so that we can write a better answer for your question.