Music share from one itunes - onto two phones (seperate accounts)

I'm trying to help my mum and dad out - they have one computer that the music is purchased from and 2 Iphones under different account names. I was wondering if there was a way I could share the music between the two phones for them. Any help would be greatly appreciated.

(p.s - the acount with the muisc is syinced with my dads phone, an I-pad and an I-nano... Just need mums phone to be able to share the music....)

Cheers 🙂