All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
You have made a conditional divorce upon helping your brother in getting a visa with clear words of divorce, and by three times divorce. Therefore, if you do so (the thing upon which you conditioned divorce) then your wife is divorced three times, according to the opinion of the four Schools of jurisprudence.
Therefore, you should not do what you conditioned divorce on, and you should not help your brother in this matter in order to keep your wife. However, you may help your brother in other matters in order to avoid the problem.
Allaah knows best.