I thought I'd add my twopenn'worth to this interestinbg thread! If the parents lived in Peel, involved in fishing, it's not so surprising that they'd journeyed to Castletown, either along the Herring Way (14 miles), or by boat. I certainly know of some social interaction of that sort, which resulted in the illegitimate birth of my great grandmother! Derbyhaven had a sizeable fishing fleet I believe.
On the other hand, if the parents were Irish, there was also some to-ing and fro-ing between the Isle of Man and Ireland, because of the Spring fishing fleets which left the island for 3 months to go to Kinsale. I believe some docked at Irish ports (for suppies?)
Good luck! Jo