Why The Name?
Millionaire No. 2 gets their name from the cocktail of the same name, The whole thing sounding fairly elegant which represents Two to me and the cocktail itself uses a dash of grenadine, one of the main ingredients featured in a Shirley Temple.
How'd They Meet?
The two end up meeting sometime around Tpot 11. When they alongside all the other exitors escape Four and end up working in the kitchen. Two becomes vaguely infatuated with this odd little glass and they end up spending some time with them. They never go anywhere with their relationship, it's fairly one-sided and they never become "official".
What about the kids?
Back in the Six Cylinder about section I mention that their kid, Bong, gets erased from the timeline which screws with everything else and erases Shirley & Six's memories of each other as in this timeline has completely differed from the "main" one. This makes Millionaire No.2 the "end game" relationship in this 'ruined' timeline. And with this, we get their kids, Melon and Sippy, who don't cease to exist after the timeline becomes corrected. Mistake children who were never meant to exist leads to angst yadda yadda.