Hayate the Combat Butler ran October 2004-April 2017 in Weekly Shonen Sunday (also inspiration for 2007, 2009, 2012, and 2013 TV anime, plus 2009 and 2014 OVAs, a movie and live-action drama). Apparently, this wasn't long enough for Kenjiro Hata to develop all the ideas he was considering. Final volumes 51 and 52 were released this weekend. The limited edition of 51 featured a bonus collection of character secrets. 52 featured a bonus collection of character after stories. One of 51's secrets is getting a lot of attention.
One of the secrets is that Nagi's maid Maria is a half-sister of Hayate.