Which person do I have to use in this sentence? <Someone seems younger than "they" are>
Hello everyone,

I made up this sentence but I don't know which person I have to use. 

Someone seems younger than they are.

is "they" correct?

Can I say: "Someone seems younger than it is or "Everyone seems younger than they are"? 


Thanks a lot

Everyone looks younger than they are. But your sentence doesn't make much sense if written out of context .