Brothers Hugh, Edward, Thomas and Bernard Costello

My gggrandfather was Hugh Costello, born about 1834, reportedly in Killashandra, County Cavan. This information came from his obituary, along with the names of his brothers Edward, Bernard and Thomas (possibly others). DNA testing confirms that I have the right family. The New York death certificate lists Edward and Bernard's parents as Patrick and Ann(a) Costello. (Ann's maiden name might be Morrow.) Hugh's New Jersey death certificate does not list any parents. His brothers were born Edward est 1815, Bernard 1825, Thomas is unknown and there's possible a sister Margaret born 1829. I find no record of the entire family immigrating to the US, but Hugh and his wife Mary Reilly (Riley) have their first child, John in 1855. I do find some ship records for a Hugh Costello traveling with others but I can't connect the names of the other travelers.
 

After many years of searching, I found Hugh's burial in New York. Along with Hugh, his wife Mary and most of their children, is an Amelia Costello who dies in NY in 1877 at the age of 78. At her death she was living with Bernard Costello, but she is buried with Hugh. I have Amelia's NY death certificate but it doesn't list her parents or her spouse, and I can't find any record of when Amelia arrived in the US but the death certificate states she was living in NY for 18 - doesn't list years or months! Hugh's first daughter was named Amelia, as well as a grandaughter. Both Bernard and Edward have headstones, but not Hugh, and the cemetery records don't define who Amelia is. I'm wondering if Amelia was the second wife of Patrick but can't find any record of her in Ireland or New York. I also don't find any Killashandra Costello records.

Other surnames include Sheriden and Sexton possibly from Killashandra too?

Any information on any of the people I've named above as well as any others that may have remained in Ireland would be greatly appreciated.

Eileen Healy