Most of the Kul Tirans have a very similar accent to the Gilneans, probably because they shared the same ancestors, and the Kul Tirans were originally from the Gilnean peninsula.
But what was their relationship for most of their history? Were they allies or enemies for the most part? Were they kind of like the United Kingdom and the United States today, or rather like the United Kingdom and Ireland?
Genn was probably sent to Kul Tiras, likely because he and his people, long isolated themselves, were probably the only kingdom in the Alliance which the Kul Tirans could easily relate to - and possibly have some remnant of affinity towards and respect for. It's also possible that he knew Katherine, as he personally knew Daelin, her husband, for many years; they certainly at least knew of each other, and he was the one who persuaded her to go seek out Jaina.
It's really interesting to ponder - perhaps the Kul Tirans could allow Greymane's people to resettle in their lands, if the Forsaken still occupies Gilneas, or if it is still blighted or abandoned for whatever reason, could allow them to reconnect somewhat and share their experiences with each other.