The Scamanders are one of the oldest wizarding families in Britain. Somewhere along the line some high ranking lord or lady from the Seelie Court bred into their line although none of their abilities have shown up in hundreds of years.

Theseus and Newt are the first descendants who gain notice of both faerie courts with their deeds...Theseus the war hero and incredible duelist...Newt the child of nature with his talent in taming all kinds of beasts...even those of the wild hunt. Both Seelie and Unseelie Court want to have such raw talent in their ranks and they'll do anything to get both Scamander brothers.

Bonus: Grindelwald is actually part of the Unseelie Court and takes an unhealthy interest in Newt after the obscurus desaster.

Happy end if possible!