Is a government employee whose salary is insufficient and who supports a large family sinful if he takes from the charity collected by his wife from philanthropists for the needy, knowing that they are needy and do not beg persistently from people?

The needy person is one who finds something, but it is not enough for him. If this is your situation, then there is no blame upon you for taking from zakat (definition), and even more so from the voluntary charities and aid that you distribute. However, if the owner of the wealth designates a specific person to whom the money should be paid, then it is obligatory upon both of you to deliver the money to the one he designated.