Jamaa’at al-Tableegh, like other da’wah groups, has its good points and is doing some good, but there are also some reservations about it. Its followers vary in their level of knowledge, understanding and soundness of method from one country or region to another. We have discussed this group previously in the answers to questions no. 8674, 14037 and 39349. Based on that, if your brother is religiously committed and of good character, and he follows the Sunnah and is cautious about bid’ah (innovation), then there is nothing wrong with your trying to get him married to your friend.
But if you know that your brother is insisting on following bid’ah or he travels a great deal, and there is the fear that he may carry on with that after he gets married, which may have harmful effects on his wife and children, then you should not intervene to arrange his marriage, and in that case he should marry someone who is like him, so as to avoid arguments and disputes.
And Allaah knows best.