Here is the family tree of the Pandavas:
As you can see, Arjuna had four wives, each of whom bore him a son: Draupadi had Shrutakirti, Krishna's sister Subhadra had Abhimanyu, the Naga princess Ulupi had Iravan, and Chitrangada princess of Manipura had Babruvahana. And each of Arjuna's four brothers also had a son with Draupadi: Yudishtra had Prativindhya, Bhima had Sutasoma, Nakula had Shatatija, and Sahadeva had Shrutakarma. And although the family tree doesn't show it, Bhima and the Rakshasi Hidimbi had Ghatotkacha. In addition, Yudishtra and Devika had Yaudheya, Bhima and Valandhara had Sarvaga, Nakula and Karenumati had Niramitra, and Sahadeva and Vijaya had Suhotra.
Now Abhimanyu, Iravan, and Ghatotkacha all died during the Mahabharata war. And the five sons of Draupadi were killed immediately after the war by Ashwattama, who thought they were the five Pandavas; he was trying to avenge the death of his father Drona. (For this he was cursed with a painful immortality.) In any case, Babruvahana was the only child of Arjuna to live after the Mahabharata war; he became the king of his mother's kingdom of Manipura. And when the Pandavas went to the Himalayas after the death of Krishna, they left the kingdom of Hastinapura to Abhimanyu's son Parikshit, the first Kali Yuga ruler of the Kuru dynasty.