I think your family member has rather misunderstand the concept of Karma and reincarnation. Two separate concepts that often get put in the same blender.
“Reincarnation” is the idea of recycling souls to further their life lessons, or, what some call Karmic destiny.
However, IMO, the concept of reincarnation has nothing to do with karma.
From my dabblings into these areas, “karma” is, simply cause and effect, in the here and now.
Whether this cause and effect is carried over into other spiritual lives is based on whether or not, we do have multiple carnations. This is an interesting concept to entertain, but, there is no substantial proof of this being true.
For reasons above mentioned, it seems unlikely, but, on the other hand we can never claim to know anything for certain.
My focus is more along the lines that if one keeps doing what they’ve always done they will keep getting what they’ve always gotten.
Meaning, if you conduct yourself in negative ways you will reap the results of your negativity, whether that is ruining relationships or ending up in prison, or dead of liver disease. If your doing unto others is less than, sooner or later you will be the recipient of the same.
The reincarnation concept is based more on the concept that ‘souls’ choose to return, in whatever form, to continue to learn and experience every conceivable experience from being born a crippled child to the experience of being a mass murderer.
Bottom line, nobody will know anything until they are dead.
Then again, as humans have multiplied, IF, there is such a thing as reincarnation, it makes sense that as more humans come into being, more would be recycled as well. haha
We are all made of the same stuff as the stars and rocks and trees and dirt, just arranged a little differently, what comes after our arrangement withers is impossible to say.