It makes sense to me to chose someone who knows the children's parents well enough to do them justice while raising their children. I have chosen my parents as my sons guardian if my husband and I should both die. I realize now that it was a terrible mistake and actually feel a bit sick and tearful now as you have brought this question up. I'm a bit panicked actually. They have no idea how to raise our son as we would! They do not appreciate our lifestyle and our style of child rearing, not to mention my mother is not stable enough to look after her own emotional needs, let alone my sons and she would ban Mono from ever seeing him again.
I think that it is best to give that responsibility to whomever would respect how you have raised them thus far and who has the closest values and believes as you. If this is a secondary partner then so be it. It makes sense to me that they would fit that bill.
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