Can the mother get custody of the children in the event of a divorce?

First understand in the state of Washington joint custody is the norm. There may be a visitation custodian and a residential custodian, but joint custody is the expected way children are to be treated. Your question is what are your chance of being the residential custodian if there is a divorce. That depends on which parent provides more care to the children. I would guess that in custody disputes, woman are awarded residential custody about 65% of the time.

You are about to sign a very important agreement that will affect the rest of your life. You need to consult with a lawyer and not try to get advice over the internet on such an important matter.

It sounds like he want to ensure that he is in the lives of his children and will have joint custody. You need to have an attorney for a prenup. Ask your attorney for advice.

It means that the court will determine who is best able to provide a loving, stable environment for the children. If the children are under 10, it is likely that one parent will have primary physical custody and the other parent will have substantial visitation. Over 10 it is possible that the custody will be 50-50. If a child has a problem with one parent, the custody may be reduced. So what it means is that if there is a divorce, you will both go to court and explain why you think your custody arrangement is best. Of course, it will also be possible that the two of you will agree as to the custody arrangement. However, your attorney that is advising you on the pre-nup should provide all of these answers.

I would be cautious about planning for a breakup prior to the marriage. See an attorney and explain all of the circumstances.

You should have any prenuptial agreement looked at by your attorney before agreeing to it for many reasons, this is just one of them.