I used to think altruistic surrogacy (for a family member or very close friend) to be an act of kindness.
Very similar in fact to a kidney donation in the instance that both carry risks.
Though I've always been opposed to commercial surrogacy.
Now I'm not so sure.
For a start we're not talking about an agreement between 2 consenting adults who are aware of the risks in the case of a transplant.
Re: surrogacy there is a child in the middle of this who has no say whatsoever if things go wrong.
Equally, there are often other children in the picture (the surrogates) who I can't believe don't experience some sort of confusion over mummy being pregnant with a child that is not related to them or indeed is related to them but will never be their sibling. They also have a lot of skin in the game if anything goes wrong - even relatively common but debilitating issues like PND or even PTSD.
I also now feel that altruistic surrogacy is rolled out as a reason why it's a good thing and in that sense it becomes a gateway for accepting commercial surrogacy as the same.
I know it's something I couldn't do even for someone close to me.
A child is never a right nor is it a gift to be given.
I'm obviously very sympathetic to people suffering with infertility (and have had several miscarriages before finally successfully conceiving my DS) but I feel more and more strongly that surrogacy isn't the answer.
In a way OP the fact you are considering this demonstrates your female socialisation - to help, be kind and put not only your DB/SIL in front of your own best interests (and your children's) but also potentially an unknown woman.
You say adoption is problematic because they live abroad - well perhaps that's a measure of how much they are prepared to invest in having a baby in the sense they could return to the U.K. or make a decision to make their current location a permanent home. Or in truth is that they want a baby that's biologically theirs?
There's so much that could go wrong as others have posted even if the pregnancy and birth go well.
I think you are potentially considering a beautiful hypothetical scenario where you "gift" DB and SIL with a child and everything is awsome and you are a "special" auntie.
But what if they divorce and it's not amicable and you never see this child again? What if you disagree with their parenting style?
What if you miscarry? How many "tries" are you prepared to go through?
From having IVF you know the commitment in terms of medical treatment/appointments - time you'll spend away from your family that might be magnified by multiple attempts.
What if there is pressure on you to provide a sibling and a rift develops because you "selfishly" won't do it again?
So very many ways for this not to bring joy to a family but heartache.
I'm genuinely sorry for your DB and SIL but I honestly don't believe you acting as a surrogate is the answer.