en_tn_condensed/1jn/03/10.md

In this the children of God and children of the devil are revealed

This can be stated in active form. Alternate translation: "This is how we know the children of God and the children of the devil" (See: rc://en/ta/man/translate/figs-activepassive)

Whoever does not do what is righteous is not from God, neither is the one who does not love his brother

The words "from God" are understood in the second part of the sentence. This can also be stated in positive form. Alternate translation: "whoever does not do what is righteous is not from God; whoever does not love his brother is also not from God" or "those who do what is righteous are from God, and those who love their brothers are from God" (See: rc://en/ta/man/translate/figs-doublenegatives and rc://en/ta/man/translate/figs-ellipsis)

his brother

Here "brother" means fellow Christians.