1)
Why does it now teach the seed of Yerachmi'el?
1.
Radak: Ezra first taught about Ram ben Chetzron, for he is primary to teach about David's family. After it taught about Kalev ben Chetzron. Now it returns to teach about Chetzron's Bechor, Yerachmi'el.
2)
Why does it say "Yerachmi'el ha'Bechor Chetzron ha'Bechor Ram"?
1.
'Rashi': Because the Sefer interrupted to teach about Kalev's family, it needed to teach that Yerachmi'el was Chetzron's Bechor. Malbim - Ram was Yerachmi'el's Bechor.
