A:
If the reality is as mentioned in the question, it will be Wajib (obligatory) for this man to fulfill his vow. This is because
he made the vow conditional on being granted a child and this actually happened. The matter of whether that child (Part No. 23; Page No. 248) would live or not was not considered. Moreover, the reason for making the vow was that the husband was not granted children. Regarding of his being Faqir, he may postpone fulfilling his vow until Allah (Exalted be He) gives him out of His abundant bounties.May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.