You can, but you quite possibly know already that she is hiding them from you before you thought of getting married. (?) Not going to be much of a family if you aren't allowed to be with her and her kids if you get married. Find someone else without problems like this.
You can marry, but the marriage may have problems down the road. Make sure that you truly understand the circumstances - could be custody issues or something entirely different - before marrying. Check out the legal background of the situation to be sure.
No. You are marrying the man or woman, not their kids.
yes
Not really it depends on the man and the woman's gens
He did not have kids, nor did he marry.
You seduce a male vampire causing the woman to be pregnant with a vampire child or you could have a male sim marry a woman vampire and get her pregnant to cause the same results.
No.
no
If they are both honestly following their hearts and being true to themselves, LOVE will conquer all.
Helen Keller did not have kids or marry
He had no kids. He did not marry in fact.
no, she never married or had kids
Only if the parents split up. Otherwise, the kids would still be siblings in law, and that still counts as incest.