Reference: http://www.alfawzan.af.org.sa/node/15734
Question: What is the ruling regarding giving charity to one who does not pray, bearing in mind he is a relative?
Response: It is not permissible to give charity to him while [you know] he does not pray. That is because this is [considered to be] aiding him [upon his transgression against Allaah]. And he will understand [your charitable gesture to be a sign of] your acceptance of him having abandoned his prayer, whereas [in reality] he should be boycotted until he repents to Allaah (‘Azza wa Jall).