As Syb mentioned, you could say “quelqu’un s’occupe de lui/d’elle” ou “quelqu’un prend soin de lui/d’elle”.
“Quelqu’un est à ses côtés” or “quelqu’un est à son chevet” are possible as well.
The first two can be used in many different contexts.
The last two, especially the last one, could be used when someone is feeling ill and sick.
I hope that helps.