Answer:
Expert testimony becomes difficult when the case revolves around parent and children/siblings because their DNA is really identical, although SNP is very likely different. Although SNP are what you will be looking at since they are unique and the chances of a matching one are 1 and 8 billion. So by showing the SNP evidence in the testimony will help you overcome the challenges.
Step-by-step explanation:
Im not sure if this is what you were looking for but i tried :)