I think he was around a bit and known as Gaggi's nephew, so maybe Gaggi never had to put him on record as being with him, he was with Gaggi by default. I do not think he was as close to anyone as he claims, his stories did change over the years. He was defiantly a heroin junkie, I don't see how Gaggi or anyone else could have trusted him as much as he claims. Considering he ratted and testified, they would have been accurate.
Actually it was someone in Pat Conti crew who voted against his name being inducted and called him a junkie, others came forward and practically said the same thing. Someone close to Paul Castellano also said Montiglio was a junkie, may have been Mosca who spoke in Castellano ear, but the only other family to speak out about it was the Lucchese family. Gaggi was told his nephew was not going to be made, no mention of him suspected of being an informant, so Nino had Dominick around him most of the time, and only went to the lounge when Gaggi told him to relay messages or pickup envelopes. Gaggi put more trust in his blood family than his crime family, but Gaggi was at fault cause he thought Montiglio could handle being around psychopaths and killers, not just DeMeo crew but a few other crews. Montiglio never pulled the trigger, but was a driver for a hit and dropped off the killer's for a hit, and also picked up the killers after a hit another time. Those two are the closest that he was possible helping the ReMeo crew on his uncle orders.
