Marriage abroad and hereditary communion between mother-in-law and daughter-in-law, what to do if an agreement cannot be found?

In the event of a childless marriage and in the absence of a will, the inheritance passes by law to the spouse for a share equal to two thirds of the total, a quarter goes to the parents and the remaining share goes to brothers and/or sisters. In relation to the registration of a marriage carried out abroad, the spouse falls under the rights of succession to all intents and purposes and is protected by the legitimacy as required by Italian law.