As I understand it, your relationship with this young man had ended before you discovered you were pregnant. On hearing the news, he asked you to terminate the pregnancy and you assured him that if you continued it he wouldn't have to be involved.
You then led him to be believe that you had terminated the pregnancy to the extent that you enacted the part of woman who had recently had an abortion and gave him graphic detail of what it entailed, during which time he was "there" for you after which, presumably, you went your separate ways with you being "convinced" that you could do it alone.
Some 19/20? weeks later you have decided that you "can't do this" on your own which led you to text him on Tuesday of this week with the news that he will be a father in a couple of months' time and, having found his mother on FB, you are now canvassing opinion as to whether you should tell her even though he has specifically asked you not to tell anyone at the present time.
I imagine this young man is reeling from shock at the enormity of your lie, and the very least you can do is allow him time to come to terms with the fact that the termination he nursed/comforted you through didn't occur.
It may be that he will tell his parents himself, but in any event it is not your place to do so and I can't imagine that many dm, or df for that matter, would look kindly on a woman who has put their ds through the equivalent of an emotional wringer and, having not got what she wants from him, approaches his parents.
When your dc is born, and not before, you can claim child maintenance through the CSA. It may be that he will step up to the plate and institute contact with his dc-to-be but, if not, they will be free to seek him and other paternal family members out when they come of age.
Fwiw, back in the not too distant days when 'having' to get married due to pregnancy was as expected as it was commonplate, a friend of my dgm told her ds who found himself at the wrong end of an irate father's shotgun in a similar position that he didn't have to do any such thing if he didn't want to. At the time this was unheard of groundbreaking and caused the ds to leave town for a few years.
The ds voluntarily paid maintenance for his dc regularly and his dm scrupulously sent the exact value of gifts to the dc every birthday and Christmas that she gave to her other and subsequent dgc. The dc in question was made aware of his df's name at an early age and sought him out when he was 16. Father and son have an excellent relationship and it's remarkable how much the dc resembles his df in temperament as well as physical looks.
As with giving birth, certain matters can't be hurried and you are best advised to wait for time to bring resolution, or solutions that haven't yet come to mind, as trying to force it at this early stage may result in unwelcome repercussions.
Also fwiw I suspect that this young man will shortly seek you out, not least to verify that the texts you so recently sent him are not more lies on your part.
Dc don't need grandparents; having loving and caring dgps is a blessing but having dgps who aren't particularly enamoured with the dc or its dm can be a curse.
Relax, OP. Enjly the run up to giving birth and know that what will be, will be.
By way of clarification, abortion does not have to be a surgical procedure and, if the MAP has not been obtained or fails to work, it is a default option for failed contraception which, in some cases, is essential for the emotional and/or physical wellbeing of the women concerned, Ledkr. I rejoice that it's legal, otherwise we'd be back in the days of medically unqualified backstreet abortionists with high risk of permanent infertility and worse.