1. How much do they inherit - me 50% and them the other 50% divided between them? Or 25% each and me 25%.
Assuming that you are married under community property rules, 50% of community property belongs to you. Upon the death of a spouse, his 50% and any non-community property he may have, will be inherited by his children in equal shares. The wife is not considered an heir of her 50%. It belongs to her from the time it was acquired during marriage. This is important because of inheritance taxes. The children must pay inheritance taxes on what they receive (if they reside abroad, a 50% surcharge on taxes due applies). The wife doesn’t.
2. It was actually my money which bought the various properties and the business. I assume that makes no difference.
It may, under certain circumstances too complicated to post here. Do you work independently from your husband? Were the funds the product of the sale of your separate property? Consult an attorney.
3. Some are in his name, some mine and some joint. Do the children inherit everything or just those in his name and 50% of those in joint names? If everything is put in my name do they then not inherit anything?
It does not matter in whose name the property was recorded. If it was acquired during marriage, it is community property and the children of the deceased spouse have the right to 50%.
4. I assume it is no point in him making a will? He has one leaving everything to me - but no doubt it would be overruled by the law of the land?
Incorrect. Because of forced heirship rules, you will not be able to get the whole estate as in the U.S., but your husband may leave up to 25% of his share to you.
5. Could their mothers get involved even if they are over 18?
No, assuming there is nothing pending from old divorces.
6. Could they sign a paper now, to say that they waive their right to inheritance if their father dies first (I have a will saying he inherits from me, so if I pop my clogs first then he gets everything anyway and I have no kids, Dominican or any other nationality!). We could get them to sign something saying they waive their rights to inheritance on his death but will get everything when I die later????
Under Dominican law all agreements or contracts regarding a future inheritance are null and void (Art. 1130 of the Civil Code).
I urge you and your husband to consult with an attorney specialized in estate planning. If you have properties in the U.S. and the D.R., attorneys from both countries should be involved.