I am reading Bibek Debroy's english translation of Harivamsha. Chapter 8 of this book says that Vivasvan (Sun) had 3 children. 1 daughter - Yamuna and 2 sons - Vaivasvata prajapati and other is Shraddha-deva prajapati.
Bibek Debroy mentions in footnote that Shraddha-deva is Yama (God of Shraddhas).
Out of those two prajApati-s one is vaivasvata prajApati, because he is the son of vivasvAn, namely the Sun himself while the other is shrAddha-deva, presiding deity of obsequial oblations, namely yama, or also called shamana, the eternal silencer and the girl is a twin sister of yama, named as lady yamuna...
Now, Srimad Bhagvatam 8.13.1 says that present manu is Shraddha-deva.
So considering Harivamsha, one would imagine that Yama = Shraddha-deva = present Manu = Vaivasvata Manu.
Sanjná, the daughter of Viśwakarman, was the wife of the sun, and bore him three children, the Manu (Vaivaswata), Yama, and the goddess Yamí (or the Yamuná river)
Now my confusion and question is: Out of 2 sons of Vivasvan (Sun) who is Manu of present manavantara?