My questions are: did you consider an abortion? If not, why not? And you mention that your DCs fathers family live abroad. Is he of a different cultural background to you?
I did consider an abortion, but not really that seriously. I always knew I wanted to have children and after years of struggling to conceive in a past relationship I didn't take it for granted that I would be able to again. It was pretty good timing for me in terms of my career and financial position, which helped. And actually when it was still early enough, I didn't actually know the full situation (although I did know I had got pregnant accidentally with somebody I didn't know well, and wasn't in a serious relationship with!)
Yes, he is of a different cultural background. I don't want to say what exactly but it's a country where in past it might have been considered acceptable for a man to have multiple wives/families.
Do you ever think about what would happen if he died unexpectedly?
Yes, I have thought about this a lot. Financially, he has taken out a relatively small life insurance policy in my name (which I have to trust that he continues to pay, but I'm sure he would). I am financially independent anyway though. Emotionally, well - that would be it. We wouldn't go to his funeral as it would be beyond inappropriate, and for this and many other reasons it would be extraordinarily traumatic. It's also possible that something would happen to reveal our child's existence - e.g. that one of my messages would be read, or something similar.
I think what would worry me about it is that it is usually easier for children to adapt to a situation if they grow up with it rather than it being sprung upon them later.
In the sense that whatever the situation if the truth is known by everyone including the child so if, say the father chooses to have no contact, the child grows up with that and knows no different. This is certain to come out at some point - even worst case scenario at his funeral - and I think a sudden reveal in later life can be more damaging for everyone involved - not just your child but his other children and wife. It's a hard one and I don't envy you OP.
As I've just written above too, I definitely wouldn't feel it was appropriate to go to his funeral if anything happened to him. If our child was older then I suppose it would be their decision but I would strongly dissuade them as I don't think it would be in anyone's best interests. That is even assuming we found out about it before it happened!
I completely agree that a sudden reveal is likely to be more damaging for anyone involved. Hopefully our DC will become more emotionally ready to learn more about the situation at some point (they aren't now, which worries me, so I haven't broached it with them although in some ways I would imagine that it is becoming obvious that something is weird. Nothing has been asked though).
Of course, in an awful way I know I am lucky that I have the option of telling my child gradually and in the most sensitive way I can. There will be other shocks and repercussions for them later in life but I can lay some of the groundwork and hopefully avoid at least some of the damage. I feel terrible for his wife and family, who don't have any knowledge and therefore real choice. But also it makes me feel very reluctant to tell anyone anything, as it would bring their world crashing down. And who really wants to do that to somebody?