Firstly, the Law will over ride any legal agreements that Bob and Jane make. Bob and Jane will have to adhere to the normal family law rules in terms of access, guardianship, maintenance payments, custody etc etc. The Law will not allow either to opt out of any responsibilities.
Secondly, you mention that Bob & Jane are x's. So they have a past history of lack of compatibility? If they are such good friends, and so compatible, that they want to have a child together, and keep their lives so intertwined, you would think that their relationship would very effortlessly transform into a loving relationship with marriage, children etc etc following? So why hasnt it?
When couples with children break up they deal with it as best they can but most people would agree it's far from ideal, why on earth would you engineer this situation?
Also i'm curious as to the motive of the post, is this a real life situation or just a topic for discussion? No harm if it's just theoretical discussion, i'd just be amazed that people could think this plan would be a good idea when you could think of the amount of people that could end up hurt by it, and that's not even taking into account the child if they find out the circumstances they were conceived under!
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I had given up a child for adoption when I was very young, so I needed to go through some "stuff" before I could contemplate having more children...
As it turns out, we cant have children. Part of me is upset, but really I have learned through life, that I can only be happy when I accept things the way they are. Some times we can get into a flap wanting things we cannot have, this can be material things or emotional things.
Why not think ahead and ask the child would it rather be born into a normal family, or be born to two self-obsessed idiots?
The child wouln't exist either way as only Bob and Jane can produce said child...
Honestly, I don't think its a good idea, and not fair to the person being born. I understand Jane's maternal urge to have a child, however she has to comprimise and fully understand her options. She wants her cake, and she wants to eat it too.
if Jane thought with her brain instead of her ovaries, this story would be first of all about her consideration for the child she'd like to conceive. how will the child perceive the relationship between her and the father. will it need/miss the father figure in his/her life? there's plenty of questions asked from the child's point of view but it would need two people who are not obsessed with themselves.