What is "Того" in the Bratja(Братья) [Fullmetal Alchemist] ?

In this case means "who." The last two lines in the first verse could be translated in English like this: "There's no point to try to bring back one who has been taken by the Earth" Probably the meaning is clear but I'll make it more clear - One of the brothers has died and the other said this sentence.

Well, from the text of the song it is not quite clear who has died whether it is a brother or a mother.

Well, you're probably right. The mother has died, actually, but the translation is correct, anyway.

Thank you very much.
Their mother has died.
I corrected my translation.