I would judge both - he's a lying, cheating cunt, and she's scum too. The cheating is more down to him, of course, and I do agree that in cases where it's married woman there often doesn't seem to be the same "manipulative man seduces helpless woman" narrative. (Wrongly - I would judge a single man sleeping with a married woman just as harshly). And regardless of whatever this woman's plans, intentions, seductions etc - she didn't have an immaculate conception by willing herself pregnant with his child. He chose to cheat, end of.
Of course there are exceptions - if the single person has been lied to and told their partner is single too, and cases where one partner is married but genuinely separated. (Some would still count as cheating- I don't).
FWIW, I do have sympathy for men in a committed relationship whose partner says they are using contraception - while it's not rape, it's manipulation and deceit of the highest degree and completely different to an accidental pregnancy. But if a married man is willing to leave the contraception to his bit on the side then he has to right to run crying when a pregnancy is the result.
That doesn't change the fact that this woman is utter scum. For intentionally setting out on a course of action she knew would destroy a family (including wholly innocent children), for lying about contraception. And for putting her selfish desires above what's best for the child she so desperately wants. That baby will have a possibly reluctant and resentful father, damaged and hurt half-siblings, and be born into the middle of an emotional war zone. And heaven forbid the child find our the story behind their origins. This entire mess will be the legacy given to an innocent baby. Why, when there are alternatives?
@Lozz22 
I am sorry for your losses, honestly - no one ever deserves that.
But, with all due respect, surely there are so many other ways to fall pregnant that don't involve dropping a bomb on your baby's life before they are even born?