Hanuman ji Lord Hanuman is son of Vayu Dev(Wind God) and top most devotee of Lord Ram. Lord Hanuman has not any sister but he has one brother, very famous Bhima.

Bhima had born with the power of wind God as Queen Kunti and Pandu can't have children because Pandu was cursed.

But Queen Kunti was blessed with Mantra given by sage Durbasa by which she can call any demigods and asked any benediction. For Bhima she had called wind god and asked son from him. So, In this way Lord Hanuman and Bhima were brothers