First, if the meaning of being the Son of God is a true meaning, in accordance with the Muslim belief in God, who is inconceivable in terms of any defects, flaws, combinations, needs, limitations, and issues of this kind, it cannot be plural.
Second, if we consider this term metaphorically - such as becoming divine and purifying the soul - then it will not be specific to Prophet Jesus (peace be upon him) and will include many believers.
Third, if the description of Prophet Jesus (peace be upon him) with this title is due to the special creation of Prophet Jesus (peace be upon him), this title is much more suitable for Prophet Adam (peace be upon him).