Are the family of my deceased sister-in-law entitled to claim their daughter's movables, given the existence of a furniture list, after her death and the presence of a two-and-a-half-year-old child, and my brother's desire to remarry?

If the furniture list is owned by the wife and considered her Mahr (dowry), then after her death, it is considered an inheritance to be divided among the heirs according to Islamic law, based on its current value, not the value written in the list. The wife's family is not entitled to claim all of it, but only their legal share. If the husband wishes to keep the movable property, he must give the other heirs their rights. In this case, the husband receives one-fourth due to the existence of a descendant heir, the daughter receives one-half, and the remainder is divided among the other heirs.