It is totally different after death, as that must be according the inheritance laws of the Shari`ah.
A boy gets twice as much as a girl and girls get equal shares regardless of being married or not.
In giving gifts during one’s life time, a parent should give his/her children equal shares regardless of their gender or their being married or not. It should be the same for boys and girls and no difference between married or single sons and daughters.
But, in inheritance, it is to be distributed after death. A boy gets twice as much as a girl also regardless of being married or not.
Another issue may be related to this. If a parent spent on the marriage of a child, and there are other children not married yet, he/she should also spend on their marriage in a similar way.
Parents cannot make this in their last will because it will affect the obligatory shares. I believe that one must make a gift to the unmarried equivalent to what she/he spent on the marriage of others.