I think [name_f]Rosalie[/name_f] or [name_f]Rose[/name_f] fits best. [name_m]Classic[/name_m] but also another nature/noun name, plus it shares sounds/letters with your boysâ.
Other suggestions (I like the nautical meanings/noun theme so these all fall under one of those categories):
[name_f]Jenna[/name_f] [name_f]Rosalie[/name_f]
[name_f]Maren[/name_f] Rose/Maren [name_f]Rosalie[/name_f]
[name_f]Luna[/name_f] [name_f]Rosalie[/name_f]
[name_f]Gali[/name_f] Rose/Gali [name_f]Rosalie[/name_f]
[name_f]Rianne[/name_f] [name_f]Rose[/name_f]
[name_f]Isla[/name_f] Rose/Isla [name_f]Rosalie[/name_f]
[name_m]Gale[/name_m] [name_f]Rosalie[/name_f]
[name_f]Skyler[/name_f] [name_f]Gracelyn[/name_f]
[name_f]Solana[/name_f] Rose/Solana [name_f]Rosalie[/name_f]
[name_f]Ondine[/name_f] âDinaâ Rose/Ondine [name_f]Rosalie[/name_f]
[name_m]Ocean[/name_m] [name_f]Rose[/name_f] (ârosa rugosaâ is a rose variety also called âbeach roseâ as it grows on beaches in various countries.)
[name_f]Oceana[/name_f] Rose/Oceana [name_f]Rosalie[/name_f]
[name_f]Oceane[/name_f] Rose/Oceane [name_f]Rosalie[/name_f]
[name_f]Bay[/name_f] Rose/Bay [name_f]Rosalie[/name_f]
[name_m]Albie[/name_m] [name_f]Rose[/name_f]
[name_f]Coral[/name_f] Rose/Coral [name_f]Rosalie[/name_f]
[name_f]Brisa[/name_f] Rose/Brisa [name_f]Rosalie[/name_f]
Ann-Marie Rose-Ann-Marie [name_f]Rosalie[/name_f]
[name_f]Summer[/name_f] Rose/Summer [name_f]Rosalie[/name_f]
[name_f]Maribeth[/name_f] Rose/Maribeth [name_f]Rosalie[/name_f]
[name_f]Alba[/name_f] Rose/Alba [name_f]Rosalie[/name_f]
[name_f]Mari[/name_f] Rose/Mari [name_f]Rosalie[/name_f]
[name_f]Marilla[/name_f] Rose/Marilla [name_f]Rosalie[/name_f]
[name_f]Maribel[/name_f] Rose/Maribel [name_f]Rosalie[/name_f]
[name_f]Maribella[/name_f] Rose/Maribella [name_f]Rosalie[/name_f]
[name_f]Marielle[/name_f] Rose/Marielle [name_f]Rosalie[/name_f]
[name_f]Mariel[/name_f] Rose/Mariel [name_f]Rosalie[/name_f]
[name_f]Mariela[/name_f] Rose/Mariela [name_f]Rosalie[/name_f]
[name_f]Mariet[/name_f] Rose/Mariet [name_f]Rosalie[/name_f]
[name_f]Mariette[/name_f] Rose/Mariette [name_f]Rosalie[/name_f]
[name_f]Marila[/name_f] Rose/Marila [name_f]Rosalie[/name_f]
[name_f]Marietta[/name_f] Rose/Marietta [name_f]Rosalie[/name_f]
[name_f]Marion[/name_f] Rose/Marion [name_f]Rosalie[/name_f]
[name_f]Marisa[/name_f] Rose/Marisa [name_f]Rosalie[/name_f]
[name_f]Marissa[/name_f] Rose/Marissa [name_f]Rosalie[/name_f]
[name_f]Marnie[/name_f] Rose/Marnie [name_f]Rosalie[/name_f]
[name_f]Marley[/name_f] [name_f]Gracelyn[/name_f]
[name_f]Marley[/name_f] [name_f]Rose[/name_f]
[name_f]Meli[/name_f] Rose/Meli [name_f]Rosalie[/name_f]
[name_f]Meri[/name_f] Rose/Meri [name_f]Rosalie[/name_f]
[name_f]Merrill[/name_f] Rose/Merrill [name_f]Rosalie[/name_f]
[name_f]Naia[/name_f] Rose/Naia [name_f]Rosalie[/name_f]
[name_f]Muriel[/name_f] Rose/Muriel [name_f]Rosalie[/name_f]
[name_f]Miriel[/name_f] Rose/Miriel [name_f]Rosalie[/name_f]
[name_f]Mirren[/name_f] Rose/Mirren [name_f]Rosalie[/name_f]
[name_f]Moira[/name_f] Rose/Moira [name_f]Rosalie[/name_f]
[name_f]Morgan[/name_f] [name_f]Rosalie[/name_f]
[name_f]Morgana[/name_f] Rose/Morgana [name_f]Rosalie[/name_f]
[name_m]Seabrooke[/name_m] [name_f]Rose[/name_f]
[name_f]Brooke[/name_f] [name_f]Rosalie[/name_f]
[name_f]Selkie[/name_f] [name_f]Rose[/name_f]
[name_f]Ula[/name_f] Rose/Ula [name_f]Rosalie[/name_f]
[name_f]Pearl[/name_f] [name_f]Rosalie[/name_f]
Also, a couple more boysâ suggestions:
[name_f]Firth[/name_f] âarm of the seaâ
[name_m]Rory[/name_m]
[name_f]Ro[/name_f]
[name_m]Royce[/name_m]
[name_m]Dalton[/name_m]
Sanderling (another seabird)
[name_m]Reed[/name_m]
[name_m]Reid[/name_m]
[name_m]Doyle[/name_m]
[name_m]Irving[/name_m]
[name_m]Rafferty[/name_m] âRaffâ
[name_m]Gale[/name_m]