I don't know about the warden or hawke but I believe we'll most definitely be related to morrigan
The child is always produced at the end of witch hunt no matter how far you go out of your way to try and prevent it, ogb or normal.
The child is suppose to be a catalyst for "the change" that is to come.The catalyst/hearld/savior is always the protagonist.
The child is being trained by morrigan to handle its world shaking destiny.Why would a npc need training to fight? Bioware would never give a npc a bigger destiny than the protagonist.
Only a male warden that morrigan was in love with can acompany her which requires you to have slept with her at least once as a mandatory prerequisite thus always producing a child unless you had alistair take your place but either way, baby is born.Morrigan will replace leandra and the warden will most likely replace malcom hawke acting as some Father/Adoptive father.
There is also an interesting line in origins where morrigan tells flemeth "I hear the peace of the grave is eternal" and flemeth responds "Bah! May your child one day treat you the same".I concluded from this that gaider plans to have morrigan become a semi/old woman with a adult child at some point.
I wouldn't put it past bioware to make us flemeth's estranged grandchild giving us the choice to finish what mother morrigan started and become the herald to her plans.