it is not true. Spouse and each child have the equal right.
Article 1144
Each spouse has the right to inherit the property of the other, and his or her entitled portion is determined according to the following Subparagraphs:
(1) Where the spouse inherits concurrently with heirs of the first order, as provided in Article 1138, his or her entitled portion is equal to the other heirs;
If OP’s father and his wife didn’t make any special aarrangement, half of property and assets they got after their marriage are spouse’s. The remaining half and father’s own property and assets which he got before the marriage are inherited property. If there is no will, each of spouse and two children has a claim of 1/3 portion.