If you see anything of your brother/sister that pleases you, or someone in his family or of his property pleases you then ask Allah to bless him in it, for the envious eye is real, say:

اللّهُـمَّ بارِك عَلَـيه ما شاءَ الله، لا قُوَّةَ إلاّ بالله

O Allah send blessings upon him. (This is) that which Allah has willed, there is no power except with Allah.

[Ahmad 4/447, Ibn Majah, Malik. Al-Albani graded it authentic in Sahihul-Jami' As-Saghir 1/212. Also see Al-Arna'ut's checking of Ibn Al-Qayyim's Zadul-Ma'ad 4/170]