As is the way with Disney films, Anna and Elsa's parents are offed before the plot of Frozen really gets going. They're presumably killed in a shipwreck, although this theory suggests they survived a little longer than that.
Tarzan, the last great film before Disney's decline in the early naughties, opens with a couple and their young baby shipwrecked on an island, ultimately murdered by a leopard. Rather than a random seafaring couple, this duo are actually the King and Queen of Arendelle; they survived the storm from Frozen and found themselves stranded.
The timings all match up; both movies are set in the same time period (ish), there's some visual similarities between the parents (imagine Anna's father with a bigger moustache and you have Tarzan's Dad) and if the couple were at sea for a while it's conceivable they could have had another kid.
It's not just an inconsequential link though. Assuming Arendelle's monarchy is the standard for the time, that makes Tarzan the rightful king. Boy we hope that doesn't get Elsa too angry.