All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
If you did not specify a certain beneficiary for your vow, as is apparent from your question, then it is incumbent on you to give the vowed money to the poor and needy, even if they were your relatives. In fact, giving charity to one's poor relatives is better and entails more reward. The Prophet, sallallaahu ‘alayhi wa sallam, said: "Giving charity to a poor person is charity, and (giving) to a relative is charity and maintenance of the ties of kinship." [Ahmad, An-Nasaa’i, and Hibban; At-Tirmithi: reliable] Of course, we mean by relatives in this context any family member aside from one's parents. If one's parents are in need of money to provide for themselves, then the son is obliged to help them financially and provide for them. In this case, it is impermissible for you to give them the vowed money in substitution for the financial maintenance that is due upon you for them. If they were not poor and do not need money, then they are not entitled to receive the vowed money as well because they are not among the eligible beneficiaries of the vow.
Allaah Knows best.