I think you should either go with [name_m]Yoan[/name_m] or [name_m]Jonny[/name_m] but I am not liking them together in the same name. I know [name_m]Yoan[/name_m] is a Catalan form of [name_m]John[/name_m] but it comes off as more feminine as it is too similar to [name_f]Joan[/name_f]. I don’t know where in the world you are though, if you are in an Hispanophone country then it wouldn’t matter. Maybe [name_m]Joaquin[/name_m] as an alternative? You can still call him [name_f]Jo[/name_f] for short.