Thanks for posting your query.
I am Dr.R.K and I am pleased to assist you.
Coffee ground vomitus may indicate a bleed inside.
I presume he passes only normal colored stools.
You can check his hemoglobin level.
If the recurrent coffee ground vomitus is due to bleeding, then there would be a drop in hemoglobin.
If it is really a bleed and the quantity is more, he would pass black tarry sticky offensive stools.
If these two confirm bleed, then the cause of bleed should be found out.
An upper GI endoscopy may be done to find the cause.
I hope that answers your query.
Let me know if you have any more questions.