poor younger sister, her children likely won't be alive before their grandparents are dead, leavung virtually all grandparent like duties to the son is a shitty move.
honestly lefi needs a more matured body to match her personality, whuch can probably be done with magic. Apart from that their relationship is really well developed, feels like they've spent years together.
So is tachibana affected by the female biological clock? This might determines how far they could potentially go with the genderswap theme. F for jingujis sanity.