By the way, Maca and I live in a house with two other adults (my sister and boyfriend) and soon to be a 3rd adult (friend in crisis) as well as 3 "kids" (oldest is 18, but still in highschool) and soon to be a 4th (child of friend in crisis).
As much as it SOUNDS impossible-it's very possible to have a large family with an odd mix live together as a family.
NOT saying you should do that NOW. NO WAY.
But don't discount the possibility that IF you and Mary build a TRUE loving friendship AND you and your husband build a healthy happy strong marriage AND he remains in love with both of you, that you couldn't happily live together and very productively raise all 4 kids.
The kids tend to be the EASIEST part to integrate!