Wouldn't using the grandmother generally be better in these cases? Generally speaking one's grandfather is one's actual grandfather but not always.

Only if the child was a girl. Maternal DNA, MITOCHONDRIAL DNA, is passed down female to female. So a daughter will carry her first female relative from the very start of her line, from 10,000 years ago, in her DNA. VERY COOL!! Paternity, establishes the male DNA of the child and needs a male relative. So, you can use an uncle, the dad's father, or the baby's grandfather to check paternity.

Dear god. That is not how it works. You cannot be serious? https://www.nytimes.com/2016/06/24/science/mitochondrial-dna-mothers.html

Dear goodness! You are so touchy! I made a mistake and put the wrong thing down should have been saying maternal dna. That will teach me to post late at night! But you could use a lesson in kindness and an attitude adjustment when an error is made! Wow. You were really rude to me and very “omg you have to be kidding me?!?!” Way. So first, thank you for pointing out my mistake and second go fvck yourself for being a really rude b***h in the way you did it. Havent you ever mixed up your topics and been thinking of one thing and wrote another?? I’ll be watching! 👀😁 Are not a nice person in my eyes.

The father is not dead in this case.

As someone who's be bogged down in the cort system I can say Rhyme is probably right. There probably isn't a way for them to prove either way about the consent and you wouldn't even know for a few years at least. In circumstances like this the best course of action is probably to live your best life and keep them out of it. At most file a restraining order?