Y'sena has a good relationship with Mufasa and Scar is friendly towards her, but can get annoyed and lash out. She's younger by a long way, being only a cub when Mufasa marries Sarabi (Which I think happened a long time before they had Simba and were crowned rulers)
The RP would start when Mufasa meets Sarabi for the first time and continue untill...whenever

Anyone interested?