Hi Lady Fatima:
God is not incapable of anything, he does not need a Son to help him, that wouldn't make God, God. Thats not exactly what im trying to say.
God has a Son because he is self-less, not self-ish. Tell me a reason why he doesn't need a Son or doesn't need more than 1 persons or different forms of himself to do different things?
This can be quite confusing at times Anyway ... would you like to give me any reasons not to have a Son and what's bad about it?
Its just like saying Why does God have or need Angels if he is capable of doing things all by himself, so if Allah can everything by himself, why has he created Angels, and if he can make Angels, why not have himself in more than one form or character and have a Son?