Is it permissible to lie, claiming to invest money, in order to give some of it to a needy brother, and is that considered usury?

It is preferable not to take money from your brother under the pretext of investing it and then help him with your own money, to avoid future contradictions and doubts. Instead, try to help him directly while explaining to him that this assistance is due to the bond of brotherhood and kinship.

If you are unable to convince him to accept direct assistance, there is no harm in taking the money from him with the intention of investing it, provided that you intend thereby to show kindness to him and earn reward, and that you keep the original money as a deposit for your brother. This is not considered forbidden lying; rather, it is permissible in such cases that aim to reconcile and do good.

In this case, the money is not considered a loan because you took it with the intention of keeping it as a deposit, not with the intention of benefiting from it.