In this canto of the Shrimad Bhagavatam Yajña Who is identified as Hari married His uterine sister Dakṣiṇā Who's identified as the partial avatāra of Lakshmi.
So They had the same gotra
Even if the boy's gotra changed with Manu adopting him they were still born of the same mother's pinda(womb).
How come the marriage is valid, then?