"And then, of course, there's a couple that claim to be, but I haven't done any DNA tests or anything"

This quote by Merle Haggard is most likely referring to a circumstance in which there are individuals who claim to be related to him, however he has refrained from doing any DNA tests to verify the relationship. This might be translated as an indication of caution on his part, as he is not going to accept the claims of these individuals without evidence. He may be worried that they are not really related to him, or that they are attempting to make the most of him in some way. It could likewise be translated as an indication of regard for his own personal privacy, as he does not wish to share his personal details with strangers. Whatever the case, it is clear that Merle Haggard is not going to take any opportunities when it comes to his household and is taking the essential steps to guarantee that any claims of relation are legitimate.