How do you feel about creating fictional members of real families?

In a project that I am currently working on, I have a character who I am envisioning as a fictional member of the House of Bonaparte. This character was born in 1957 as a fictional 4th sibling to the living Napoleon VII who has 3 siblings in reality.

How do you feel about this concept? I know that there is a relatively un-common concept in fiction of historical figures having fictional descendants but this feels like something different entirely and I feel like it may be inappropriate as the aforementioned concept of giving historical figures fictional descendants only works if there is no one left alive to be offended by it.