Thanks for posting your query here.
Major health problems in babies are not due to same blood group
of their parents. It is usually due to problems with genes their parents are carrying. If both the parents are first-degree or second-degree relatives and both have minor DNA/Genetic problems, the baby gets the disease.
It is very advisable to get blood testing of both the potential partners before marrige especially looking to find out Thalessemia trait. If there are any other disease running in the family or unexplained early deaths, that also need to investigated so as to avoid child having such diseases.
Occasionally, despite all these precautions, babies are born with major health problems.
So, in summary, major health problems in children is not associated with same blood group.
Dr Tejas Shah