Hi Bill, Some of what I have on that family line came originally from Max. Lorne Greville, who often posts to this list is also of this Halpin line, and he also gave me details of persons on that line. Perhaps if you did a post asking him if he can assist, you may get more from him.
I notice in Max Heywoods website that he shows the Will ofHenry Greville d:1796and in it it shows amongst other things " mother Hannah NUGENT", so his mother apparently later married into the NUGENT family.
Now Baron Greville of Ireland changed his surname to Greville-NUGENT so he could inherit. His wife was nee Rosa NUGENT, SO as Christopher Fulke Greville who also posts on this list is apparently of that Greville-Nugent line, then a post asking him if he knows of any tie in you may get more from him also. Regards Ralph G.