Is it permissible for me to continue taking money from my father's friend, given that my siblings are now working, while I am still a student abroad with my mother?

There is no harm in taking money that comes without being asked, as the Prophet, peace and blessings be upon him, said: "Take it if anything from this money comes to you while you are neither covetous nor asking. Take it, but do not pursue what does not come." There is also no harm in continuing to take it, even if the recipient is wealthy.