Berth and Berthina (although I wouldn't go for these myself)
Bernard and Bernardin or
Bernard and
Bernardine
You see, I'm not really sure if you want boy-boy, boy-girl or girl-girl, but here's more:
Bevan and
EvanBowen and
OwenBrys and Brysthach
Cadell and Cadellin
Cas and Casnar
Cas and Casswallawn
Clust and Clustveinydd
Nessa and Nessan
Dylan and
DylanEva and
EvanAlar and Alara
Dryw and Drywson
Dru and Drudwas
Alyn and Alyna
Govan and
GovannonAedd and Aeddan
Jon and Jones
Jon and
JonahJon and
JonnaLlwyr and Llwyryon
Mab and
MabonMael and Maelona
Mael and Maelogan
Mael and Maelon
Maelon and Maelona
Math and Mathonwy
Medyr and Medyredydd
Ol and Olwydd
Penn and Pennar
Sel and Selgi
Sugyn and Sugynedydd
Ceri and
CeridwenIsa and
IsabelPaul and
Paulina