My assumption is that Ann is related to Ban and Elaine. And we know that Ann's real name is Anghalhad which could be as Galahad, so according fo Arthurian's legend. Maybe Ann is one of the kinghts of the round table(?) as we know that Percy is one, and of course we shouldn't forgot Lancelot, who's the child of Ban and Elaine, he is the prince of the lake. And another knight is of course Meliodas' son, Tristan, the other knight that possess the power of darkness and light
(⊙…⊙ )This topic may contain spoilers
According to Arthurian legend, Galahad is the son of Lancelot and Elaine of Corbenic (different woman from his mom).
I know it sounds SOOOOOO wrong, but if Lancelot is her real father, than the only person who could be her real mom is Jericho! In side story 6, Lancelot and she disappeared and reappeared years later, so who knows how long they've been isolated from everybody and when they returned. Her power must be from due to her fairy heritage, her light blue hair from Ban, her quick reflects and sword attacks are like Jericho and..... In chapter 18 she revealed her suit and she looked almost identical to Jericho's new design! Part of me doesn't want to believe it, but the evidence here is too strong to ignore!

Now that I saw the cover photo of this chapter, that girl named Anne has the same hair color with Ban and also her magic is related with mind reading which is Elaine’s. Maybe did they have second child?