You'll need the authorisation of the father to take the children back to the netherlands, and allow ample oportunity for him to see the children, including sending them here for vsits during the holidays.
The fathers authorisation can be supplied by a judge if he denies authorsation for futile reasons.
Taking the kids to the netherlands without proper authorisation, or retaining them without such authorisation (holidays but never go back) would result in a dutch judge sending the kids back to Brazil where they had their usual residence based on the 1980 treaty of The Hague.

Originally posted by sven You'll need the authorisation of the father to take the children back to the netherlands

and that applies equally to overseas travel even if you are still happily married! I'm happily married in a strong relationship and am taking my kids to London next week while my wife fies to SP on business. However, I still need her written permission (stamped by the PF) to take my kids out of Brazil as she is not accompanying them. Basically, both parents need to be travelling with the child or give their written consent for the child to travel without their presence.

Basically, if you do divorce and it's not amicable, you will be at his mercy to grant assent for your children to leave Brazil temporarily or permanently.

Better to work hard as staying happily married.

Originally posted by Lilly1980 ... Say, we get married, have children and all ... what would happen to the children if we would get divorced for some reason and I want to go back to my home country?

I've met hundreds of men who came to Brasil with no kids, money in the bank and life by the balls ..... and BAM! The next day that Guy as 3 munckins and a Crazy Brasilian wife making his life a living Hell on Earth! I suppose some men just have a bad case of the dumb ass.