The fact is, there is no such a thing as the biggest or reddest or shortest or longest or smallest thing. At one stage, atoms were supposed to be the smallest thing. Then electrons. Then protons. Now quarks are supposed to be the smallest thing. How strange. Charmed, I'm sure. From top to bottom.
The planet was once thought to be the biggest thing. Then the solar system. Then the galaxy. Then the universe. Now they are fooling with the word "universe". What we once thought of as the universe is now said by some to be part of an ensemble of universes called the multiverse. And said by others to be a baby universe---one of many (an infinite number of) offspring of a universal parent.
Words lose their meaning when they are applied to different things than those to which they formerly were applied. The word "universe" is a good example. Once upon a time the word "universe" meant: "Everything." "All of it. Without one single little bit left over." "The whole bang shoot." "The whole shebang." Then cosmologists and other horse thieves put forward hypotheses about the nature of the universe and what it represents, including, for example, the hypothesis of the multiverse, Everettian or otherwise. But, but, but. Say the hypothesis of the multiverse is true. Then, the word "universe" ("everything") should be applied to the thing called "the multiverse." And we would then need another word to describe that which we previously termed "the universe". Maybe we could call it "the infinity formerly known as 'the universe'".
Infinity is a strange, strange beast. Just ask Georg Cantor. Some things are more infinite than others. Well, strictly speaking that is not correct. What I mean to say is some infinities are bigger than other infinities. Some infinities are smaller than other infinities. As Cantor proved, the real numbers are "more numerous" than the natural numbers.