Can he get rid of interest by giving it to his brother who is in debt?

Firstly: 

Putting
money in the bank for interest is emphatically forbidden, and is a major
sin. Allaah says (interpretation of the meaning): 

“O you
who believe! Be afraid of Allaah and give up what remains (due to you) from
Ribaa (from now onward) if you are (really) believers.

279. And
if you do not do it, then take a notice of war from Allaah and His Messenger
but if you repent, you shall have your capital sums. Deal not unjustly (by
asking more than your capital sums), and you shall not be dealt with
unjustly (by receiving less than your capital sums)”

[al-Baqarah 2:278-279]

It is not
permissible to put money in a riba-based bank except if there is the fear
that the money may be stolen etc, if there is no other means of protecting
the money except by putting it in the bank. In that case it is enough for
him to put it in a current account that does not bear any interest, because
in cases of necessity, things that are ordinarily forbidden may be
permitted, but only to the extent that is necessary. 

Secondly: 

If a person
has engaged in riba, then he has to repent to Allaah by giving up the sin,
regretting what he has done, resolving not to go back to it, and getting rid
of the haraam interest by spending it on charitable causes. He is not
allowed to benefit from it himself or spend it on those on whom he is
obliged to spend. 

Shaykh ‘Abd
al-‘Azeez ibn Baaz (may Allaah have mercy on him) said: With regard to the
interest that the bank has given to you, do not give it back to the bank and
do not consume it yourself; rather spend it on charitable causes, such as
giving it to the poor, repairing public washrooms, and helping debtors who
are unable to pay off their debts. End quote from Fataawa Islamiyyah
(2/407). 

Thirdly: 

It is
permissible for you to get rid of this interest by giving it to your brother
who is in need, on condition that it is not obligatory for you to spend on
him, so that that will not be a trick to enable you to benefit from it and
save your own money that you would spend on him if you had to. A man is
obliged to spend on his brother if three conditions are met: 

1-The one who is spending would
inherit from the one on whom he is spending if the latter died. But if the
brother would not inherit from his brother because the father is there or
because the brother has a male child, then spending on him is not
obligatory.

2-The brother on whom he is
spending is in need and is unable to earn enough to make him independent of
means.

3-The one who is spending should
have wealth that is surplus to his own needs and those of his wife and
children.

If these
conditions are met, then it is obligatory for a man to spend on his
brother. 

See also the
answer to question no. 6026. 

Fourthly: 

There is
nothing wrong with getting rid of this interest by giving it to your brother
to pay off his debts, even if it is obligatory for you to spend on him,
because a man is not obliged to pay off his relative’s debt in all cases,
whether it is his father, brother or anyone else. Hence the most correct
view concerning zakaah is that it is permissible to give zakaah to parents
and siblings to pay off their debts, as was the view favoured by Shaykh
al-Islam [Ibn Taymiyah] and others. 

See:
al-Ikhtiyaaraat al-Fiqhiyyah, p. 104. 

For more
information, see question no.
39175. 

Conclusion:
It is permissible for you to give the interest to your brother to pay off
his debts, whether you are obliged to spend on him or not. 

As for
giving him the interest to spend on himself and his family, not to pay off
his debts, that is permissible so long as it is not obligatory for you to
spend on him. 

And Allaah
knows best.