Aruch HaShulchan, Laws of Tzedakah, 251:16

I am truly perplexed by those authorities who believe that when one gives money to tzedakah, their poor relatives should automatically be the prime benefactors of the contribution, and that one can therefore designate their tithe to their poor relatives. Many disagree with this principle, as I found in a statement of the Mordechai: I have found that one who gives coins to the tzedakah fund may not distribute them solely amongst their poor relatives because the giver is obligated to distribute the money equally to all the poor of the town. It is also stated in a Tosefta: One who orders ‘give a coin to the poor’ - the giver must give it to the poor of the town - until here are their words...One authority says that this ruling applies to the money that the Torah obligates you to give, but if one wants to donate additional money, then it can go towards that person’s poor relatives. And in my humble opinion it seems that regarding all of these cases, the court shall decide (how to allocate the money) as they see fit, because in all matters pertaining to tzedakah and donations to the community, we go according to the estimation of the giver’s intentions. [Translation by AJWS]