As per Vishnu Purana: Part1: Chapter 15, in Vaivasvata manwantara, Brahma's son Daksha incarnated as Prachetas' son. As Daksha's mother Márishá was daughter of Soma (Chandra, the Moon god) and daughters of Daksha were later married to Chandra so he was both maternal-grand-father and son-in-law of Daksha's this incarnation!
Daksha's daughter Vasu was married to Dharma. The eight Vasus named Ápa, Dhruva, Soma, Dhava, Anila, Anala, Pratyúsha, and Prabhása were sons of Vasu. Varchas was son of Soma.
Varchas incarnated as Abhimanyu as Arjuna's son in Mahabharata. As per Abhimanyu's death: Was he destined to die at a young age? post and wikipedia article, Varchas was son of Soma (Chandra) which has conflict with the above description from Vishnu Purana which says that Varchas was son of Soma (Vasu).
What is the connection between Soma (Vasu) and Soma (Chandra)? Is there any mention of Soma's (Chandra, son of Atri) incarnation as Soma (one of Vasus, son of Vasu)?