Is registering the apartment in the name of the two daughters forbidden (haram) and a violation of God's law regarding inheritance, especially since he has not yet been blessed with a male child?

If the intention behind registering the apartment in the daughters' names is for them to inherit it after death, and not as an immediate gift during life, then this is a bequest to an heir, which is invalid unless approved by the other heirs, according to the hadith: "There is no bequest to an heir unless the heirs wish it." However, if it was an immediate gift during life and was taken possession of such that they can dispose of it, then it is permissible. The intention behind the gift must not be to deprive other heirs.