What element would Genasi children of mixed element parentage have?

Two of the players in my campaign are Genasi, who are expecting a child. I’m doing research into Genasi’s for this new side plot. Although I’m not sure what element(s) they would have.

One parent is a water genasi, while the other is an air genasi. So would the child have both air and water, only one, or some combination of both?

I’ve researched but I haven’t been able to find a solid answer, most I’m getting is linked back to para and quasi-genasi, but that doesn’t answer the question either.

Any information would be useful and very helpful.

I’m running a 5th Edition campaign, that uses older lore as well as current lore.