Qfyilyi

Mr. A had lost his son. years later he is in hospital bed trying to recover an accident. a boy comes to him and talks. The boy's name matches with his son and Mr A thinks he looks like his son. Mr. A talks about a bracelet that he himself made out of gold cuz he used to be a goldsmith and the design was straight out of his brain. The boy also talks about his bracelet and shows him the bracelet.
it is the same bracelet but the boy had been adopted by another family so he doesnot know about his biological family.
My question is what would Mr.A do or say when he realized the boy is his son?

There's not a whole lot of context here, so I can only really guess what's going on. I assume this is for some work of fiction, be it a play or a novel or the like? (I don't think this is exactly the forum for this sort of question, but I may be interpreting it wrong.)

There are a number of directions you could take this depending largely on the previously-established nature of the character. If he is sentimental and emotional, you could always describe an animated look on his face, tears in his eyes, a shaky voice, etc as he comes to the realisation. If he's a stern or 'macho' character, you could describe a subtle shift in the way his eyes are set, making them soften and move more dynamically, as opposed to a flitting, formal, studious gaze. The nature of the description should rest entirely on previous character development and if you want to show the realisation rather than narrate it, facial features indicative of emotion, less-obvious social ques of body language, etc are your friends.