Hi Tim , I would have thought the IGI christenings for Jane and Esther , since they are both from Church Records and not from a member of the LDS church , is about 99% chance of being sisters. Although there are a lot of Cross's on the IOM , it is not a common name - on the 1881 census , most popular names - Cross is not in top 100 , Qualtrough is ranked 73 with 29 families named , Kell(e)y is first with 409 , Corlett is fourth with 236 families.
For your interest my wife has a Jane Qualtrough as her 4 x grt grandmother , but not the same one , her Jane was christened 13/4/1773 in Rushen , to John Q and Margaret Q , Margaret had been married to William Q first , and her maiden name was Crebbin , to confuse matters more , "our" Jane married Thomas Qualtrough of Kentraugh in 1794.

Cheers
David