If God wanted to have a son, He could have chosen whomever He willed from among His creations. Be He glorified; He is God, the One, the Supreme.
لَو أَرادَ اللَّهُ أَن يَتَّخِذَ وَلَدًا لَاصطَفىٰ مِمّا يَخلُقُ ما يَشاءُ سُبحٰنَهُ هُوَ اللَّهُ الوٰحِدُ القَهّارُ
law araadal laahu aiyattakhiza waladal lastafaa mimmaa yakhluqu maa yashaaa’; Subhaanahoo Huwal laahul Waahidul Qahhaar