Not him, but I've seen a couple other magical girl shows from Toei. It was probably a decision from on-high and not by the creative staff.
Toei has a thing in all of the magical girl shows they have creative control over to make the 'main' heroine the only sister/child. This goes from the stuff they made in the 90's all the way up to Pretty Cure.
The rationale behind it, stemming back to producer interviews, being that it makes it easier to 'self-insert' for the purposes of selling toys. They have gimped entire stories in their shows before to meet this end. This also applies to unique origins (being created in a lab accident instead of having a mother and father) and super powers (being able to lift and throw entire mountains instead of just being a stronger version of themselves).
They have actually destroyed more than one series of theirs before by taking a competent pitch and tearing out something important to the story to make the main character more relateable. I'm sure this sounds familiar.