. . . I've finally found the Mulvaneys! I was expecting to come across them living much closer to the John Mulvaneys than they actually were, though, as addresses aren't listed in the 1865 NYS Census, I don't actually know how far they were away, geographically, just that they were many pages away. The writing on these pages are very faint, so I'll tell you that the Mulvaneys are the second family on the right side of the page. James is listed as 46 and Bridget as 50. Thomas is 11, John is 8, Patrick is 6, Mary Ann is 3, and James is a month old. Bridget says she's the mother of 5 children, so it appears that all of her children are still living at the time. Both parents have been married only once, and James is still a carpenter. He has been naturalized, but Bridget is still an alien. (I'm going to have to do some research on naturalization laws in the nineteenth century; a wife was apparently not automatically naturalized by the fact of her being married to a citizen.)
This was from page 136 of the 12th Ward of Brooklyn in the 1865 NYS Census on the FamilySearch Pilot Site.