I got this achivment only having All compain's Apart from Lily ( The Quest was there)

How it happend,

I had Only Raul with Me I travelled to his shack fired him, so he could repair my stuff then re-Hired him, i then got a popup Saying Achivement unlocked "The Whole Gang's Here" With Me still to Get Lilly

(Im not Sure if this happend with other Compaions)

Happened to me as well and don't you mean Companion?