How do you Compare Children with the Same Name?

In order to do this, you'll need either a while or a repeat loop to go through a for loop and look for the child constantly.

For a better explanation, let's look at this example code:

local GroupOfBricks = game.Workspace.GroupOfBricks --Gets the model that the bricks are in
local LargestBrick -- Variable we will use to store the largest brick
local LargestMass = nil --Variable we will use to store the largest brick size

while wait() do --loops continuously
	local Children = GroupOfBricks:GetChildren() --Gets the bricks
	for i, Brick in pairs(Children) do --Loops through all the bricks
		local Mass = Brick:GetMass() --Gets the size of the brick.
		if Mass > LargestMass then --Checks to see if the current brick is larger than the largest brick
			LargestMass = Mass -- Updates the mass variable
			Brick.Name = "LargestBrick"
			LargestBrick.Name = "Brick"
			LargestBrick = Brick -- Updates the largest brick variable
		end
	end
end 

You can either use this code and edit it to fit with your game, or you can write your own code similar to this. Anyways, if you do it correctly, I believe it should work.

Hopefully this helped you out. If not, or if you have any further problems / questions, please leave a comment below, and I'll see what I can do.